Earlier quoted context omitted.
Apparently Steam games are favourite attack vector of NSA, they love exploiting Steam games on sysadmin machines. https://www.wired.com/2016/01/nsa-hacker-chief-explains-how-...
No Sysadmin shoud be playing games on the systems he/she uses for admin work.
Heck, back in the day I caught someone (thankfully not at the place I worked) running a game (some FPS) server on their exchange server box. Running Steam is well within the realm of possibilities.