I think a bit of the problem is that you can't hide spamming pmods because they go through the filter. Its that and player moderators have a sense of trust about them or generally do to atleast newer players to the game. Since it is possible to get scammed dicing (not that uncommon for large gambles) and a player moderator role presents trust, then a player moderator dicing sends the message that dicing can be trusted and Jagex doesn't want that to happen. Not entirely my views on the subject but how it is explained to us and why Jagex won't let player moderators dice. Now that is quite a bit offtopic, but in an attempt to be on topic: Their are a handle full of top players that are moderators and dicing has shown to be a good source of gp (check the prayer histores XD), so its near a point for high ranked players that if they want the quick and easy money of dicing they will have to trade in the crown, which is a bit of an unfair choice in my opinion, but meh. Another angle to money making problems I guess.