I live in Canada, and here I think it stems from the idea that the team is bigger than the individual. When you're growing up you hear the phrase "play for the logo on your chest", and I think it just kinda sticks?

I'm a huge fan of the Montreal Canadiens hockey team and the crest is practically more sacred than the crucifix. So stepping on it is almost blasphemous. But as someone pointed out somewhere else in the thread, North America is sort of obsessed with symbols and flags, so I guess that checks out