This is a really great question. Interesting that most people here seem the opposite to me. Follow up Poll on how this relates to grey/demi-romo/sexuality and where the correlations are? (sounds very technical)
For me it is actually my sexuality. It seems more relevant to my life that I can be sexually attracted to all (or rather any) people. If I want to engage sexually with someone I simply make sure it's mutually un-romantic. If I were to encounter a situation where I particularly wanted to be with a person but they wanted something romantic, I would probably have a discussion around my general lack of feelings in that department, but would be willing to engage romantically for their sake (if that's what I wanted to do). Honestly I feel platonic bonds very strongly so it isn't so hard for me to 'fake' romantic action as I'm very tactile and affectionate with friends so to do so with a romantic/sexual partner wouldn't be difficult.
If I were to focus more on my romantic orientation I'd likely be keeping people at a distance that wouldn't allow for the strong sexual and platonic bonds I particularly aim for so would be counterproductive.