why does homerism exist?

Specifically, why do fans always wish their college team's players to be on their NFL team, too?

I have some theories, but why do you think? Here are some of my thoughts (nothing groundbreaking)

1) People watch their team all of the time and ONLY know their team. Hence, when it comes to demonstrate their knowledge of football, their only ammo is their own players. And they think this is legit knowledge.

2) Psychologically, consciously or subconsciously, they cannot fathom the idea of not being able to pull for their player when it might hurt the Saints. If the player is on the Saints, that solves all of the problems.

3) People like taking the homer role...getting a pseudo-celebrity status on a message board ...as Tulane's #1 fan, for example.

If I get some decent answers maye I will even make a poll. It has to be better than my other ones:)