Prime example: There was no reason for the Browns to move from Cleveland to become the Ravens, or the Rams to move from St. Louis to LA.
The Rams moved (back) to LA because (among other things) there wasn't enough support for the team in St Louis. They consistently had one of the lowest average attendances in the NFL and regularly under-performed in terms of revenue generated by the franchise. If the franchise isn't generating as much money as it should, and there's an offer on the table for a move that they predict will make the franchise more profitable then that's a perfectly valid reason is it not?
I don't like it and hate the way teams in America move around, but to say there's "no reason" is just plain wrong.