You are trying to bring logic into football which doesn't exist.
If you are looking at it empirically there is no reason for anyone to support a bunch of men in shorts kicking a ball of air. We do it for emotional reasons, not logical ones.
Also, if you are talking about people working in corporate jobs moving, I don't think any company has a fanbase like football clubs do, so who exactly would be upset? Plus if you do join competition, many times you are basically burning your bridges with your current employers. This is the same happening here, just at a larger scale with more people involved.