Apples to oranges.

There are varying contracts because the fan base demands it. Can you imagine the uproar if Warriors's fans found out that the organisation refused to pay Steph Curry more money when his rookie contract ran out, and then he bailed? That would have been it for them and they would have been tanking for the draft lottery. And when the team is trash nobody but die-hard fans go to watch the games or watch them live.

Fan impact upon the NBA, NFL Soccer etc is huge. They represent a far far bigger portion of the revenue than that of e-sports leagues which are primarily funded through advertising, and prizes which are also funded by advertising.