I can understand you don't see the need for it, and I won't be claiming that I'm in the majority nor that Jagex has to do that. But what exactly (If you leave the amount of time Jagex would have to spend on coding this) would bother you about non-PvP worlds? No matter what, I cannot think of anything that would trouble anyone except griefers. You yourself consider them douchebags, so why in particular don't you like the idea(Or rather, why aren't you indifferent about it)?