What does the launcher do with regard to the operation of the game that cannot be done within the actual game itself? Is it due to a technical limitation or simply there for the convenience of the players? Are there alternatives to such methods of starting the execution of games?
It usually makes it easier to centralize authentication. But more importantly (from the company’s perspective), it gives the game producer a chance to upsell other products and micro-transaction content.
Don’t forget that the game producer can now collect and sell data on their customers’ systems.
With no privacy laws on the books in the USA, there’s literally nothing stopping them, and a lot of incentive to do it.
This.