I think there's a difference between thinking you can't see 30fps>60fps and just being happy with 30.
I own a gaming PC, and can see 60fps, and like 60fps, and if I saw two games running side by side running at both frame rates I'd pick it out easily, but if I'm playing a game which is designed to run at 30fps and maintains a solid 30fps, it honestly doesn't bother me at all. I wonder if a lot of those who say they can't see the difference just don't care about the difference.
I own a gaming PC, and can see 60fps, and like 60fps, and if I saw two games running side by side running at both frame rates I'd pick it out easily, but if I'm playing a game which is designed to run at 30fps and maintains a solid 30fps, it honestly doesn't bother me at all. I wonder if a lot of those who say they can't see the difference just don't care about the difference.