Some systems have issues with installers for various apps for various reasons. Steam isn't installable on every PC (and that includes not working on some modern hardware, not just that your system specs are too low or something).
Some people have issues with Steam for other reasons as well (like the fact that Valve has been knowingly refusing to fix issues causing their launcher to be a health risk in some cases).
Plenty of reasons to be glad that the game will eventually be coming out elsewhere - it has a store page on Epic (yes, Steam is actually bad enough for some people to make Epic look good by comparison).