Because how your team looks, and therefore how you look when inevitably you buy their gear, is part of the excitement of being a fan. Seeing guys decked out in the teams uniform is evocative of Sundays, of hope, of glory, of excitement. How the uniforms look can go some way to creating your identity and that of the team, and when you are a fan these things just matter.
So that's some of why.
Happy to assist Waw....
The latter point may be right. I mean, who are you really excited about on this team?