In order to play some online games that requires anti cheat.
I avoid these titles myself. In fact, I don't run wine, steam or game console emulators on my Linux workstation. I run Windows VM:s for isolation and security.
You may have strong opinions on anti-cheat software and they may be correct, but it is required for playing certain online multi-player games, and people want to play those games on Linux too (especially the Steam Deck, I would presume). Ergo, people want anti-cheat software on Linux.
I avoid these titles myself. In fact, I don't run wine, steam or game console emulators on my Linux workstation. I run Windows VM:s for isolation and security.