I think we all know that some people are more sexual than other as a general rule. And then, on top of that, one person will be more or less sexual at different times. I think the two are different though.
A person who is sexual might be more or less sexual depending on the partner, circumstances and way they see themselves. However that implies being sexual to begin with.
While the asexual communities seem to have some "range" (as in, the minimally sexual are welcome too, from what I know), it seems to me they mostly do not have a switch that could be turned off or on. I have no sexual attraction to women, and don't believe that it's about any self-image issue. Some don't have any sexual attraction to men. Some don't to either.
For me, the hard thing is dealing with it in everyday life, because I tend to be heavy on innuendos and talk about sex, and I might feel awkward in case they'd rather not talk about it, or simply would not "get" it.
But I don't think having no sex drive means they're flawed. To me, that's just the way they are. Sure, biologically we're sexual beings, but we're also supposed to reproduce, and that doesn't prevent people from being gay, right? I don't know, it's a minority for sure, but that doesn't mean they're "flawed" or need to be "treated".