WoW is this way too. The difference is that WoW is a highly segregated game, casual players will never talk to elite raiders, and elite raiders never talk to anyone outside of their guild. In fact I often used to get the advice "if you join guild then you don't have to worry about PUGs and other players anymore and can just shut off the chat channels". That is I have no doubt that raiders in WoW think that WoW has few casual soloers.
In LotRO though we're all more chummy with each other and a casual soloer can be in the same kinship as a regular raider and they'll talk to each other civilly. PUGs work in this game because we're not so uptight about how good or bad the other players are and don't start bickering fights over who should and should not roll on an item.