There are also arenas and guild sieges every night, so there is PvP on PvE servers as well. The PvP on PvP servers consist mainly of:
a) High levels ganking in low level areas

Low level twinks with 10k HP ganking in low level areas
c) High levels killing people at AH/AFK
d) Low number of individuals who spent countless hundreds/thousands on the game and have 50k HP and 1-shot people with 20k HP
It's rare to find any meaningful PvP where both sides have some chance of winning. Also with recent buffs to real gear, you can't just seal jewelry and a couple pieces while wearing Agg'd CS items anymore, so you either spend the money and risk having to spend a lot more money if you die and drop, or just wear crappy gear and be really weak.