This is an extremely complex and interesting question. The answer is even more complex.
As mammals, and especially as primates, our bodies and minds have evolved to desire, seek and receive comforting touch. At every stage of our development as individuals, and as part of a community, it is inarguably healthy for our bodies and minds. It is, in fact, integral to our very survival.
I think that, in order for touch to feel good, it must meet two criteria:
- The person being touched is honestly receptive, in the positive sense, to that touch; and
- The person providing the touch has the intent to, on some level, provide “comfort” to the person they are touching. (This can have different connotations for different people in different situations).
“Let’s start at the very beginning; a very good place to start…”
Engaging in comforting touch is something that is a primal driving force for human beings and primates, in addition to all mammals, and (surprisingly) avians. For mammals, it begins in the womb, as the first sensory neural network develops. This neural network then continues as the basis for the development of the central nervous system. This system, of course, is key to experiencing touch, as we can’t feel what we are anatomically and physiologically incapable of feeling. This is shown in a study of warm, comforting touch between married couples . We require comforting touch from the moment of birth, through the entirety of our lives, and even up to the moment of death. Whether we receive that touch or not has a great impact on our overall well-being.
A great deal of research has determined that our bodies and minds require such touch in order to function properly. However, the variables in development regarding neurotransmitter levels and cultural parameters involving touch are still being studied in depth. The neurotransmitter/hormone oxytocin has been dubbed both the “love hormone” and the “cuddle hormone”, because it becomes highly expressed in the brain during comforting and/or erotic touch. Endorphins, the “feel-good” neurotransmitter/hormone is also highly present during physical interactions that make us psychologically or physically comforted or “attended to.” 
The differing parameters of sensory sensitivity levels have been accurately and somewhat humorously depicted in the following educational pictogram of the sensory “homunculus”:
(Image credit: www.mhhe.com)
The human sensory net‘s “input parameters” are heavily loaded in favor of areas specifically developed and utilized in various stages of life, which translates functionally into sensory systems required for learning, and ultimately, survival.
What specific examples can be found in different stages of life?
As a fetus:
– touch of skin into the amniotic fluid, sac, womb, and surrounding/enveloping anatomy/physiology, to determine spatial parameters, due to the developmental nature of the integumentary (skin) system, in primary relation to the development of the central nervous system.
“From early days,
Beginning not long after that first time,
In which, a Babe, by intercourse of touch,
I held mute dialogues with my Mother’s heart
I have endeavour’d to display the means
Whereby this infant sensibility,
Great birthright of our Being, was in me
Augmented and sustain’d”
– William Wordsworth
The Prelude, 1850, II, 1. 265-272
As a newborn:
- Touch and smell, predominantly, of the mother (or whatever caretaker is most present)
- Rooting mechanisms in physiological/psychological reaction and behavior, in order to find FOOD
- Regulation of heat/cold independent of the mother
If any of these needs are not met, discomfort will result, and subsequent developmental, psychological, and behavioral complications will occur.
Through early life, ages 1-12:
Comforting touch is absolutely required for positive and functional development of the body and mind of the toddler, through to the adolescent. Positive, comforting touch from a parent or primary caregiver forms sensory feedback associations in the body and mind that set the course for positive inter-relational associations in their future, including dating, mating, sex, and parenthood. The effect of early comforting touch has been shown to help with early learning of physical comforting of friends, bonding of friends, development of communication with known or potential friends, and simple nonverbal, interpersonal communication (via facial expression and “body language”).
Early adulthood: ages 13-21:
At this stage, the young adult will have developed physical, psychological, and social awareness in relation to experiences gleaned from earlier stages of life. We are all works in progress. We take what we intuitively feel, then we take a chance via social experience, and then we process what happens. We either learn from these experiences or progress our awareness and forthrightness, or we become stuck in conceptual and social feedback loops – which can eventually “jump the fence” and progress anyways. Or not. These years are most often our first stages of sexual experience. If touch has not been recorded in our bodies and minds as “good” at this point, there’s trouble for the person. It can be changed, in one’s psyche, but the body is a bit harder to reprogram. Patience, understanding, and a willingness to affect change within oneself are paramount. It sounds trivial and easy, but it’s not.
Mature adulthood: ages 22-? (The next boundary in age is usually “senior”, age 60-70+, but it is variable):
These are the years when body awareness, habits, and customs reach their fruition through repetition. We are hopefully “comfortable in our own skin”, physically, psychologically, and socially. We not only rely on the ingrained senses of self and familiar patterns of interaction with others in order to survive and mature, but we also, as parents, are in the position to set the stage for our children in the same stages we ourselves have gone through. In fact, these experiences are so ingrained, not only in action and thought; they have made their way into common parlance of everyday experiences. Consider the phrases, “Rubbing people the wrong way,” “Having a prickly or abrasive personality, or alternately, a soft touch, or magic touch,” “Someone having to be ‘handled with kid gloves,’” “Someone being touchy, or thick/thin-skinned,” “Someone being ‘out of touch’ or ‘having lost their grip.’” Even a deeply “touching” experience is described also as “poignant (Middle English directly from Old French “poindre,” by way of Latin “pungere,” meaning to prick or touch). Metaphor for touch in language is deeply ingrained in us. Why? Because language is one of our main ways to communicate our experiences as a person.
Which also leads to the obvious: SEX and the human experience.
“Sex has been defined as, ‘the harmony of two souls and the contact of two epidermes.’ This elegantly emphasizes a basic truth: the massive involvement of the skin in sexual congress. The truth is that, in no other relationship is the skin so totally involved as in sexual intercourse. Sex, indeed, has been called the highest form of touch. In the profoundest sense, touch is the true language of sex.” 
Touch, by the holy powers of the Gods!
Is the sense of the body; whether something makes its way in
Or when a thing, which in the body had birth,
Hurts it, or gives pleasure issuing forth
To perform the generative deeds of Venus.”
-Lucretius (c. 96 B.C-c. 53 B.C)
De Rerum Natura, II, 434
If sexual intercourse did not feel as compelling and stunningly good as it does (or can), we would have long ago become extinct.
*And in our final years, the contacts we have grown to cherish and need from ourselves and all our family and communities, in our deepest being – physical, psychological, and social, will fade, even as the memory of its pleasures will be a secret fire in the deep recesses of the mind.
 Page on lww.com “Influence of a “Warm Touch” Support Enhancement Intervention Among Married Couples on Ambulatory Blood Pressure, Oxytocin, Alpha Amylase, and Cortisol”