It's actually a question relating to what some people want to do with their computer. Most people don't run an OS because of some moral objection to other OS's but because it lets them do what they want with their device.

I don’t feel particularly chained to proprietary software just by playing games. I play all of them on Linux using open source software.

Yes, the games themselves are proprietary, but that’s because they’re primarily art pieces, and proprietary licenses makes some logical sense in that case.