I think it's reasonable that if you're going to be in front of a computer for ~8hours a day from time to time you're going to do personal stuff on it. This was especially true a few years ago when smartphones and unlimited data plans weren't quite as common.

I mean sure, if it's the PC controlling some industrial machine you're probably not expected to browse Facebook on it. But if you're some temp working the reception you might have some time to kill even if you do your work properly...

There's also the situation where you're traveling and don't want to carry two laptops from instance.