Likely people who enjoy taking a break at some point during the day and also enjoy playing ping pong? I don't see how going outside to "get some sun" is objectively any better in general.

Hmmmmm I work at a large games publisher, and it's normal that everyone plays games during lunch(1 hour lunch is normal). I usually have 30 minutes for food then play something for the other 30 minutes(currently trying to get through Dark Souls 3). I guess it's the same with ping-pong or any other in-office activity.

My attitude to a T. My workplace is for working, it's not a playhouse.