Well, there are different facets of attraction, aside from the sexuality aspect. You have have gender preference even while being asexual and you can also have romantic or aromantic preferences. Even as an asexual, some people still crave a romantic relationship with others, and may get into another relationship with someone for romantic reasons – meaning that their relationship is just like any other, only it lacks sex. In this case, people can have preference to whether or not they're straight, bi, gay, etc. So someone can completely be straight and asexual. They may not be interested in sex, but they can still maintain a relationship with the other gender just fine. I also think that it's worth noting that even if someone isn't interested in sex, they may still have it with their partner for whatever reason and still be asexual.