I said nothing of the sort. And don't swear here, it is against forum rules - post edited accordingly.
When you run any of those games from the Steam Play button,. the same launcher runs but in a Steam-compatible mode. Its purpose then is so you can select mods, DLCs, and make some game settings changes, before you go into the game. Otherwise you'd have to make those changes in-game, exit the game, and run it again for them to take effect.
Before the unified launcher each game had its own one to do the same functions (as older games like CK2, Vic2, HOI3 etc still do, for instance). Having one launcher actually uses less disk space that each game having its own, like it used to be.