I don't believe that I think most people are on the fluid spectrum for a preference for either women or men. But with that being said strictly straight and gay people exist I just think majority of people are fluid.
Society has a real issue with men being with other men while not having an issue with female experimenting with other females. Hence DL only exist with men not women. So it may seem like most people are straight but that's because society doesn't want men being with other men