The seats in exit rows are generally narrower, colder, have less padding, no underseat storage in front of you, meal tray is in the armrest, some are non-reclining, etc., etc.

Exit rows aren't Nirvana to everyone. The worst Y seat I ever had was on a US 757 flying CLT-LAX one night. Horrid. Absolutely horrid. And it was one of the last seats available. I can understand why.