Diablo's Still Always Online Despite Auction House Removal

[008Zulu_v1legacy]

I can see the cheat prevention side of the argument, but not even a little bit on the social side.

Is cheat prevention that big of a deal? I mean in multiplayer it would imbalance things, but what if you like to save the world solo style, does it really hurt anyone? Or is Diablo 3 designed in such a way that it is impossible to complete unless you are in a team?