A lot of vaginal canals have slight curves, etc. Just like men's penises, some are straight and some are curved or bendy.
Even if you have a noticeably curved penis - it shouldn't effect your sex life because there are hundreds of different positions you and your partner can try.
I think most girls would answer 'I'd prefer straight' because they're imagining a 90 degree angle curved penis but in reality that is very rare. Most penises are never completely straight and lean left or right, etc...!