Depends on the time of day. Some of the smaller shards with less PVP, they might all be in factions, but one guild might be full of people that work and therefore can only be on for a couple hours each night if that much. I did do a quick look see on some of the bigger shards and noticed that they had more activity at the gates, but there were quite a few non-faction chars, so I guess they didn't want to give up the gate guard zone benefits.