Steam, Origin, Twitch, Gog Galaxy and while it's not really a launcher, I guess, I have ScummVM to play the old Leisure Suit Larry games I have from Gog. I had Epic launcher for a bit to play the Unreal Tournament beta, or alpha, or... whatever it was and I had Bethesda's launcher installed for a while to play Fallout Shelter, but now I just play the Windows 10 version.
I'll install Battle Net if I want to play WoW, Diablo 3 on PC, or StarCraft 2, but it's been a while.
I don't mind having more than one launcher installed. I actually like not having to rely solely on Steam for everything.