Again, this isn't really something we "like" per se, but something that seems to predominate among us. According to a poll on AVEN, 93% of 261 respondents claimed to be introverted. I've looked for statistics about what percentage of the total population is introverted versus extroverted, and conclusive evidence is hard to find. However, I've found no evidence that introverts could possibly be more than 50% of the general population. From the results on AVEN, one might think that introverts are just more likely to be on AVEN. As far as people who live on AVEN 24/7, that's probably true. But these days, most everyone is online, regardless of personality type. What I'd be more likely to believe is that introverts are more likely to question their sexuality, since we tend to spend more time alone with our thoughts. Introverts are also often told they're wrong-- that they need to be more outgoing, friendly, or social. There's a big divide between America's ideal personality and the introvert, a fact that could lead to increased self-questioning. Perhaps extroverts are more likely to go along with a crowd, whether it be to a party or to heterosexuality.
Maybe the people who claim "asexuals are smarter" are actually noticing a trait of introversion: The majority of "gifted"people (IQ over 130) are introverted. So maybe those people are actually noticing a real phenomenon, although they phrase it in an unnecessarily elitist way.
I'm an introvert, although apparently not a very strong one, since I tend to get bored when I'm by myself. I also don't like being alone with my thoughts, since I come up with disturbing things like the fact that I'm asexual-- har, har. I think it's important to note that being introverted doesn't necessarily mean you're shy or anti-social. My favorite way to understand the concept is that extroverts get energy from being around lots of people, while this tends to drain introverts. For me, the level to which I'm drained by social activity depends on how well I know and like someone. I can chat with a good friend for hours, but I have low tolerance for "cocktail party"-style banter with strangers. I need time alone to "recharge" from those situations.
One problem I had with writing this post is that I have no idea what the extrovert experience of life is like. The overwhelming majority of my family and friends have always been introverts, which seems unusual since by some counts, we're a minority of 25%. However, this enabled me to better avoid what seems to be a strong anti-introvert bias in American culture. Especially in the job market, the more introverted you are, the more you will get shafted (with some flexibility based on your field, but we don't all get to be computer programmers, you know). According to the well-known article Caring For Your Introvert, extroverts have a hard time understanding introverts. However, I feel like I know the experience of being sexual a lot better than the experience of being extroverted, since I have many sexual friends but few extroverted ones. It's also worth noting that values related to introversion and extroversion vary based on culture and gender. Let me tell you, it's hard to be the strong, silent type-- and female. But apparently, introverts are big in Japan.