I would not expect a union for tennis players. Why would they even have an employer? They play by themselves, for themselves. I have never heard of a tennis player “owner”, other than obviously the tennis player themself.

And the coincidence that they earn less might have something to do with how nobody can name anyone outside of the top handful of players.

> They play by themselves, for themselves.

The same can be said of actors, and yet they have a union/guild.

> The same can be said of actors, and yet they have a union/guild.

Good point. I guess the big difference is that selling the tennis game itself simply does not bring in the revenues that acting and the NFL does.

Top tennis players earn from brand endorsements, not from simply playing the game.