It's the short-term nature of them I don't get. Football would suck if the top athletes were playing entirely different games in five years and leagues around existing sports were gone after twenty. The market need (perceived or real) for major publishers to replace their games every few years diminishes how seriously I can take them as competitive endeavors. It's fun watching greats like Brady and comparing them to other greats, and if I couldn't recall the greatness of the Cowboys from 20 or 40 years ago and use them as a measuring stick, it would be much less interesting as a fan.

Overwatch will probably be dead in ten years as a "sport". It's even more jarring with games that come out every year. There's really no reason for players to get professionally good at Battlefield 3 (Madden 14) if Battlefield 4 (Madden 17) is the same game but not. It's also less interesting as a fan.