| I've said it before, and I'll say it again, there's a HUGE difference in player motivation on purchasing of gold/items when it's not allowed. When it isnt allowed, a player may purchase gold/items because it will give them an advantage over other players. They may have more time/whatever than him, or he just may want to get ahead. MMO's are VERY competative, even in EQ on non PVP servers people would sit around banks showing off their lootz. PVP makes it even more significant. A well geared char could also do a lot more and with less people.
When it's allowed, this advantage gap gets much narrower. Since anyone can buy items, people are much less motivated to buy items since it's no longer going to give them as much an advantage.
My 2centz | 