Reason why they did it (And reason why so many more games now-a-days are requiring Steam, Origin, or Live) is to try and cut down on people exploiting the game (As in, hacking it or torrenting it)
Sure, people will still get around it, but it's still another road block. And who honestly doesn't have an internet connection these days? (I mean... sure it sucks when the servers go down, but other than that....)
Maybe if this was a decade ago, I could see a complaint, but really guys?
(Also, Level 52 Hell Monk here... and level 10 Hardcore Wizard. And I have the Nightmarish Staff of Herding ^_^)