1st: steams anti-cheat software is useless. this can be seens at rocket league (=steam-xbl-cp), cs:go and other multiplayer which have still massive problems with cheaters although they use additional solutions against >steam< cheaters. they patch against it, they use verifyed phone numbers (free prepaid?!) and they tried other things, but nothing worked. that’s because you can modify almost everything in a steam game.
2nd: say goodbye to any leaderboards if it’s cross-play with steam.
3rd: people would complain because it has to 99% only access to the steam cloud. no player would get it’s xbox stuff, in this case. ms would need a expensive deal with valve to use the xbox live (own) cloud.
That’s also a reason why Halo Wars DE has no cross-play from steam to winstore-xbl. but it was dramatic case, because it has no cross-play in general and instead of making cross-play between xbl, they have killed the winstore playerbase completely.
This wouldn’t be the case with KI, because it already has a working and cheater-free cross-play between xbl.
There is no need to destroy this.
Steam is really fine, but only for singleplayer and private multiplayer. (btw: I’m steam user since 13 years…but i’m realistic)