@Lamdarer Unfortunately it's not that simple, there is not only Steam.
Epic Game Store is quite popular know and running it on Linux is a huge pain. As for GOG games, there is no launcher so people would have to manually load their saves and think to store them back if using windows (or making backups) because there will be no cloud save.
Most MMO with their own launcher (EVE online for example won't work at all) may have issues.
The switch may be easy if you use only Steam though.