Personally it irritates me when people try and suggest possible "reasons" for non-heterosexuality. Maybe it is because of medical, psychological or biological differences, it doesn't make it any less valid. Asexuality could be the result of hormonal issues or psychological issues, "confusion" or even attention issues for all I know, but it doesn't mean it doesn't exist, isnt real and valid for asexual people or shouldn't be respected.
It makes no odds to me, the only people for whom sexuality is a concern for me are people I would consider potential sexual partners. Otherwise, it doesn't change any aspect of my relationship with that person and so is quite irrelevant.