I don't know that it's anything to do with competition, per se. I agree with Dpo that none of these players think there is a chance they aren't the best, so they just want to be on the "best team" with the most people like them. Who would be telling them they won't start/play? Not the coach - he's going to tell the player they'll have a chance right away (which translates in the player's mind into - I'll get to play). Not their friends/family/hangers on.
Most of these players have been told since they were little that they are the best. They absolutely believe they are better than anyone else at their position.
Reminds me of a story I've told on here before. I met a guy 10 years ago or so who years earlier was a really good running back at a small high school in MN. He was dominant in his conference. When he didn't get any D1 offers, instead of going D2, he walked on at the U (non-preferred if there was such a distinction back then) because he knew he was better than any of the other RB's. No matter what anyone told him, he knew he'd be starting for the U. Until his first day at Fall Camp, when he realized he was miles behind all the other RB's who were miles behind Chris Darkins. He didn't last through Fall Camp. But until the first practice where everyone else blew him out of the water in every drill, nobody could tell him he wasn't going to be great and go on to the NFL. He laughs about it, now.
