You are in what is called a "limbo" state where everyone only associates with their own, not by choice but by inheritance a) likely because they have tried to have friendships with the other sex and failed b) they like friendships with their own sex, and c) they have been brought up together, i.e. in close proximity say school/college so they consider girls as childhood mates, instead of being sexual objects and finally d) you may have to be the one who breaks the rules and show them that friendships can be made with the other sex, and that will be by far the most challenging. That is if you are interested, or you could just become part of the crowd and wait until society changes and finds females of some interest, i.e. it may have to be the visit of an out of state female and attractive, where all the male hormones kick in and you will have major problems on your doorstep:)
The hormones appear to have kicked in and kicked out because of social norms:).Some societies show latent tendencies, small town mentalities i.e. they only mature around the 23-25 year old group and then girls become of some interest. You may find that the girls are also tom boyish in appearance and are considered buddies as against girlfriends. And, the "why" is likely because they see nothing special in having a girlfriend and in a way it is kind to the girl, otherwise there will be abortions, and heart break:).
had a husband who was a sociologist who found males more interesting:).