It's not the norm; it's because most server moderators have to be split between still-running FH1 and FH2 servers. Hslan.net and WOLF are the two good servers to go on; they have admins on all the time.
I think the reason people are doing this though is because
1. In such a delicately built mod in terms of methods of play, it's extremely easy (and fun, to them) to screw up their side.
2. They think since it's not official BF2, nobody will take action
3. They dislike FH2 and they're causing as much damage as they can on their way out of the mod.