I don't know any asexual people(None that really are, at least), and I can't relate to the idea whatsoever. I have no problem with it, I just can't, in a million years, ever see myself being one. To me, it'd be like going through life without talking. Sure, I could do it, but why would I want to. Sure, I might say something I regret every now and then, but never looking like an idiot seems an unworthy prize for ignoring what is wired into the human brain on it's most basic level.
There is one thing I can comment on though. You said you don't see married couples as having lasting happiness, I'd call "Constant Happiness" a contradiction of terms. Joy is recognizable only through pain, you need the comparison or else you loose appreciation for the joy in your life, as joy is recognized as being above the norm. Trying to escape sadness is like trying to escape dying against your will, the only sure way to do so is to kill yourself. Nothing is permanent, the human race itself is finite, and reaching for infinity is the best way to make sure you never even get close. Love itself doesn't last forever, but the the mark it makes on your life, the person that it helped to grow, how it defined you, those things will stay with you till the end of your days, and even if it hurt, they may still make you a better person. Who you are, is something that can't be taken from you
This is really just a series of thoughts that occurred to me, and I don't wish it to insult anyone, or imply that they don't understand these things. If sex doesn't bring joy to someone then they should do as they wish, simple as that. I've just met a lot of people who try to escape pain by becoming numb, and to me, that sounds like a different kind of pain. You have to take the bad with the good. All I hope is that it sparked some interesting thoughts in you as well