One thing I've noticed about Prog bands ...
 

... They rarely sing about women, or male-female relationships, or love songs, or things of that nature. These are a staple in other kinds of rock and in pop music in general, but it seems to be somewhat rare in Prog. There are, of course, some songs like that, but most Prog bands I've noticed, at best, only stick an occasional song on that topic in their oeuvre.

Are Prog musicians and songwriters really that nerdy?

They are "progressive" and when you're progressive you prefer to sing about fairies or space ships...