There are many explanations to what most of you are feeling. From a psychological point of view, every brain is wired the same, but at the same time it's different. In fact the variations are what make us all different. Many of those are built while we grow. It is not unusual that when a child grows in an environment where couples fail, that child will most likely end up failing himself when establishing a relationship. Same goes for most kinds of brain growth.
Which is why we can be different.
Aside from that, there is a biological reason to our choices, who we decide to partner with, even when we think it's their personality entirely, there is a pheromone side to them, that impulsed the initial attraction. Even on this online times. Then there are the different kinds of brain "wiring" as I like to call it. Our brains carries a lot of residual content from our earlier days as primitive beings. Thus, us males have a bigger tendency to hump everything that moves. With time though, we have learned to attach this to a more reason like chart, and now we can evaluate a situation to know if we want or not. But all the stimulation will still affect us, even on situations of stress.
Women's on the other side have developed on a different way, and are just now developing their sexual nature. This was due to us a society being strongly focused on Male dominance. Fun fact of life, in the past, women used to develop big butts because nature found out that our ancestors liked them since it meant that childbirth was going to be easier. Currently, mother nature decided that due to the sex positions we do, and the lack of risk involved and some other facts, Boobs are better, so future women of the world will have bigger breast, but smaller butts.
Nature is a funny thing to study, and it explains many of our decisions and impulses. Of course, all the years we have on our backs will re-shape most of this into a perfect "ME" mold, changing what we once were.
But people should not feel afraid of not liking "sex" or liking it a lot. What should really make you worried is to be afraid of making contact with other folks. Even if you don't want to establish as a couple, meeting people is a thing that everyone needs, specially in this connected world, where this social skills are a must.