That's just how Valve's license agreement works. You publish with Steam and you grant Valve the right to publish the work in perpetuity.

The licensing deal made by movie studios does not work like that because the studios are intentionally predatory. The distribution agreements are temporary and can involve periodic payments. Literally Netflix rents movies from the studios and rents them back to you. The studios reserve the right to cancel distribution deals at any time.

When a movie or show gets removed from Netflix sucks but no as much since it's a subscription and you can cancel if they don't have what you like but what you do with something you bought