This is perhaps an obvious Queer 101 lesson, but it should be said explicitly. If you ever meet a gay person, they are not obligated to introduce you to the world of gay. If you meet an asexual person they are not obligated to introduce you to the world of asexuality. Likewise for any minority. These people are people, and they have their own lives to go about. They are not your personal tour guide.
Well that's tough. You want to learn all about queer issues, but your queer friends are unwilling to talk about it. But you're never completely shut off from information. You have the internet, you don't need to be spoon-fed.
This is important to emphasize, because it might not be immediately obvious from my own writing. I clearly like to do a little 101. I like explaining things in general. I like it to a fault.
But there are two points to make. First of all, not everyone is like me. Obviously.
Second of all, even I have my limits. I don't go around explaining my asexuality to everyone around me, because that is tiring, repetitive, and socially awkward. I also somewhat prefer talking on a slightly higher level than 101, because I'm very interested in internal queer and asexual politics. I don't much like giving remedial lessons on gayness, because that is so much bullshit. Lastly, I generally avoid the kind of 101 that involves me telling you about my private life. I think my private life has rather limited 101 value anyway.
There's an interesting question of politeness and social conventions contained within this issue. In some contexts, I like it when people ask me about asexuality. There are probably many other people who feel the same way. Other people might get annoyed at the very question. So how do you please everyone without knowing beforehand what they want? Or at least, please as many people as possible?
In principle, it depends on how many people feel in each way. If the vast majority of queers don't even like to be asked, then politeness says you shouldn't ask. Unfortunately this is an empirical question, one we have no answer for. It also might depend on what you ask, and in what context. I only speak for myself, but I don't like questions about my sexual behavior, or questions from people I don't trust.
I think the best solution is to ask (if you're interested) but not in a demanding way. Do it after you get to know the person as a person. Or maybe that's not the best solution. How can I know without knowing what everyone wants? But one thing's for sure, if you are telling people that they are hurting their own cause by not giving you the explanation you demand, then you are part of the problem.