Also, if you're going to automate bots on a large scale (for resource farming or just interfering with other players), Linux makes more sense for the same reasons it makes sense for other server based software. Combined with a lower player count, devs decide actual Linux gamers are acceptable collateral damage sometimes.

Or anti-cheats looking for unusual factors of the execution environment that might indicate cheats using DLL hooking, or just something wine does differently to windows.