Having grown up in the UK as a fan of a fairly mediocre soccer team, one thing about relegation is that it makes the end of the season almost as exciting for fans of bad teams as for fans of contenders. Almost every season my team was in contention for promotion (when it was in the second tier) or relegation (if it was in the top tier) and this was often not determined until the last day of the season. In the US, however, with MLB, NFL, and NBA teams valued in the billions and a deeply entrenched system of ownership, incentives, player control, and so on, it is inconceivable that such a huge change could ever be made.