Heh, looks like none of them could answer because they were too busy logging back into WoW.
As someone who was raiding back 'in the good old days' before even the portal to Outland was opened, I can tell you that the urge comes on strong to log back in with each new expansion.
People stop for many reasons: Bored with the current content, friends all quit playing, fell behind on raiding and don't want to slog their way back to the top, ect.
Almost all of those reasons can be nullified with a new expansion.
Also, Cataclysm has the added bonus of radically changing just about all the old terrain that WoW vets know like the backs of our carpal-tunnel stricken hands.
When you've spent literally days of your life questing around certain areas, you really get attached to them - developing favorites, preferred scenic paths and such. So to see them torn asunder has a strange emotional impact.
I've heard a horde player refer to the scene in the Cataclysm trailer where a zeplin is sent crashing into an Orgrimmar tower as "like 9/11" without a hint of irony in his voice.