I think the "Why can't I" phrases are addressed more at the question of "Why does it seem this thing is normal in current society and I am not able to do this thing with little pushback".
See, I come at this from the opposite direction. When the heterosexuals start talking about their platonic "girlfriends," I consider it a kind of stolen valour.
Edited for clarification, this comment could have seemed really nasty if read out of context.