Eventually you'll get tired of "meaningless" sex and get a feeling of emptiness, but sex is still a social experience. 
Would you say that sex is always - or primarily - a social experience? I'd say "maybe not", but intimacy is. Sex can include it or bring it but far from always does. Intimacy usually requires some degree of committed communication.
About the major question re connection(s) and happiness: What about the statistics here? Any studies anybody knows showing the proportion of people who are happy only if they are with others how much of the time and in what kind of relationships? (It sounds fairly involved, one would probably have to define "happiness" in some "measurable" way as well as some rough categories of relationships). A likely first hypothesis might be that most (a majority) are less happy if they are altogether lonely, and fewer and fewer are happy the more isolated they are? Animals make great compations for many people, pointing to companionship with living beings as important. I saw something about a little study of elderly people in nursing homes where they kept a cat and a dog; it seemed to improve their health (the peoples', I mean).
