Why pay all that and wait to play? Because that's what forced grouping is: Lots of sitting around, hoping someone else comes along, wanting to do what you want to do, praying they're of the "right" classes, so that you can actually PLAY.
Designs that hinge on being bored will do progessively worse and worse as more and more viable alternatives emerge. Compare EverQuest 2's numbers to World of Warcraft's. Both build on successful game franchises, and EQ2 builds on the previously most successful North American MMORPG. But it's also a game full of waiting to have fun, whereas Blizzard lets you head right to the fun parts. (This breaks down a bit at the higher levels, but breaking down at level 60 compared to breaking down at level 5 is orders of magnitude in difference.)
Forced grouping is a great idea, in theory. In practice, paying customers don't want to be forced to wait for what they want. On Demand and similar cable/satellite options are turning into a very nice business model because of that.