Well, good question indeed - if there would be a rollback on February 1st 2011, back to January 1st 2011, during the period I was grinding cash like no tomorrow, after just joining the discovery - I definitely wouldn't be here today.
So it's sort of "delete cheated stuff and lose some new players who didn't even have the idea of what was going on" vs "don't delete cheated stuff and don't lose these players".
I guess administration team made their decision. Although, some compensation for people who joined in and grinded stuff during that time, and now lost everything they have - would be good, imho - after all, I doubt there would be more than few tens of them.
It'd definitely require some RL time from administration team, but the newbies I'm talking could've lost incomparably more time (in some cases, possibly more time for a single person than total time it'd take to go through those 20-30 people). So no, it's not about pixels.
Veterans can cope with losing a billion or two, on the other hand, I bet, so we don't see complaints about this rollback from players who have been here for 2+ years.