What reasons do people in your groups give for not wanting to GM?

[Scrivener of Doom]

(snip) Personally, I'd rather not play, but only GM, I find being a player only as boring, and I can only last a couple of months as just a player before I lose my mind and must take the GM chair to keep my sanity.

I hear you. That describes how I feel too on the few occasions I have played.