That's different though because you actually have to go and pay the entrance fee. With esports you can just keep the stream running in the background, you can usually even mute it.
The Elder Scrolls Legends (TESL) had "drops", watching streamers play the game would give you in-game benefits. To the surprise of nobody, even small streamers (as long as they promised to host another TESL streamer afterward) had hundreds of viewers. Very, very quiet viewers who would not write in chat even once. Rebroadcasts became a thing with the biggest TESL streamer simply showing the same once recorded game-play over and over again.
Because no one had to make any effort or pay to watch the stream.
There is also a very similar thing that we have in sports: betting.
Independent sites exist for esports betting. In Dota 2 there is also betting on pro games with the in-game shards that are earned only by playing (if the player is subscribed to this program with a fixed fee).
The Elder Scrolls Legends (TESL) had "drops", watching streamers play the game would give you in-game benefits. To the surprise of nobody, even small streamers (as long as they promised to host another TESL streamer afterward) had hundreds of viewers. Very, very quiet viewers who would not write in chat even once. Rebroadcasts became a thing with the biggest TESL streamer simply showing the same once recorded game-play over and over again. Because no one had to make any effort or pay to watch the stream.