Well this can be for a number of reasons.
Most importantly it should be noted that events aren't a high priority. Actual PR work > hosting events. Additionally, events take a while to host, and this takes away from the time we could be spending actually working. I also do not host if I'm the only PR online, as there would be no one to do the reports/uploads.
Just because staff don't host when you're online doesn't mean that they're not hosting at all.