I think it is just about growing knowledge and acceptance on one side and growing need to demarcate yourself on the other. Everything is a spectrum, right?
I remember ~20 years ago, when I knew nothing of being trans-gender as a concept, and I bearly heard of some people being trans-sexuals.
These days I am fairly on board with the concept of gender as being a role in society you choose to play, that is often informed by your sex, but doesn't have to.