Because they are seriously spoiled at this point. Some of them honestly think that the entire game should revolve and be designed just for them, and $&#@ the rest of the playerbase.
Btw, the vault of OPness isn't helping either tbh.
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Catering to casuals is one of the main reasons that allowed WoW to take off as strongly as it did, especially during Vanilla/BC. I still remember many butthurt EQ players calling WoW "MMO for dummies", "World of Grandmacraft", or other supposedly witty phrases in the same vein. Coincidentally or not, the times when the game attempted to go into full Git Gud™ mode was when it started to massively hemorrhage players - the same players that fund the hardcore crowd's fancy toys.
If you want a full hardcore-oriented MMO, you can always go play Wildst... Nvm, I forgot that it tanked harder than a bag full of bricks