Because interacting with other windows users is painful.
Because gaming and gaming modding in particular is still fairly windows centric
Because many windows apps are not available on Linux, and you end up being forced to use alternatives that usually don't hold a candle to the proper one.
Because text rendering scaling is still integer based and trying to do say 120% scaling will result in a weird look.
Because having an issue on your system isn't solved as easily as updating a driver.
Because VR support on Linux is fairly non existent.
Because you'll always be a second tier citizen to the cool new apps that get released.
Linux might be a great upgrade if you only use windows for web browsing, but if you're a windows power user transitioning to Linux can be painful and in my experience primarily a downgrade.