Why? Because Eve is far more complex than the mind numbing simpleness of WoW. Seriously, most people who play WoW would not be able to handle the depth that Eve brings. Or the fact that it's skills based leveling versus experience based leveling. Not to mention other rudimentary skills that Eve requires that WoW cannot.
I've played both. WoW is mindless. Saying anything otherwise is a lie. And it's populated by some of the most immature people in the universe, amongst other addicts that dedicate far too much time to the stupid game.
Add that to the fact that it hasn't changed one bit since it's release. Sure, you have expansion, but overall, it's the same damn thing, with even less content per expansion. At least original wow had a huge world in which to level. Sure, you had levels 1-60, but it had lots to do.
Then comes BC - small amount of zones, 10 levels, the time synch of regular dungeons vs. heroic. And then raid content that isn't even released until BC is horribly dated. How long to release Black Temple and SUnwell Plateau?
And the first raid content in WoTLK? A rehash of prior OC content with Naxx. Seriously. I saw that, and quit. I was doing Naxx back after clearing BWL years back. And until Ulduar, that was all we had again, not including the stupid single boss encounters that were just Mag/Grulls rehashes. Lame lame lame.
WoW is a mindless time synch, and really does involve way to many hours, even if played casually.
I tried Eve for about 3 months, saw it could also become a huge time synch, and walked away. From a scope/scale perspective, it's far more large than WoW can conceive.