I find this puzzling. Raiding content hasn't been this good since BC. Cataclysm was about a big a joke as WotLK. I'm guessing people just forgot what it was like to have to farm things.
The actual raids themselves are the best I've seen for years, comparable to Ulduar and TBC. I really liked the first tier of Cataclysm also but I don't think many others share that view.
The amount of effort players need to put in to keep up though is completely out of hand, for anyone who read the post from Exodus/Vodka on why they stopped raiding that's pretty much what im getting at. While we didn't go the the extremes they did (I think some of the top guilds have mandatory 3-5+ characters raid ready?)
The time it takes to have multiple characters at their best... I'm talking capping valor, running lfr, doing dailys for coins, actually learning how to play it, the list goes on.
Believe it or not people actually have a job and/or study as well as all the other things normal people have to do. The effort vs reward is just... no... not worth the trouble.
This isn't just limited to 25 man either.