Because the argument for streaming services is _convenience_. And that's especially true when we're comparing them to piracy.

Having to switch streaming apps/programs every month is not convenient.

Having to wait up to a month to change services if I learn about a new show I like is not convenient.

Having to pay for multiple streaming services if I happen to like content by multiple producers is not convenient (or cheap).

The streaming industry honestly seems like a "prisoner's dilemma" like scenario. Each streaming company (presumably) benefits over their competitors by having exclusives and limiting where certain shows can be watched. But the streaming market as a whole is held back by this.