I am not sure how to even answer this question. I dont know why I am a fan of the Cardinals and have been since about 85' when at the age of 16, and just starting to get into football, liked their red unifroms. Had no ties to St Louis and until I had family move to phx later on had no ties to phx either. (I did eventually end up living there for 6 years though)
My friends are Jets, Cowboys, Steelers fans and they ask me why I support this team. I dont have a logical answer to that. But I know when I ask them why they support their teams they dont have a logical answer either. It is something engrained that I nor any truly passionate fan can explain.
Is it logical? Of course not. We, in essence, are supporting a corporation with a state/city affiliation. Players come and go. But once it is engrained, and you have it in you, it is impossible to let go. I could never support another team. (Although after the Bears game I told myself my new favorite team was the Falcons and the Cards can F$%k off-that lasted about 12 hours)
I guess if you dont have it it is hard to understand. And it is impossible to explain in a logical sense, so trying to explain to someone who doesnt 'get it' comes out as insane.....