Sega is the latest to abandon Steam. The competition from the Epic game store has been as much as a nuisance for those who have jumped in whole hog with Steam.
The developer has posted a piece on the move.
Epic also has the stigma of being backed by Tencent of China. Tencent however is an entertainment company and they are not a government enterprise.
A Total War Saga: TROY will be released August 13, 2020. Recall the howls of rage when Metro Exodus abruptly left Steam for Epic.
I agree that the fees from Valve/Steam are probably more than they should be. Steam probably runs afoul of Sherman among other laws. This is about the only legal basis to clean up the problem for everyone concerned.
Sega was stiffed by Randy Pickford back when he was contracted to develop Alien v Predator but Pickford spent most of the money on Borderlands. So most likely Sega wants to fine a safe place to sell their games. AvP has one of the shortest campaigns of any game I have in Steam.