This isn't just about MMORPGs; written literature has a similar issue.
As some have pointed out above, it's far easier to invent a story-framework when you don't have to deal with plausibility.
In our technologically sophisticated world, and especially among gamers, we have a territorial claim on technology and scientific plausibility. We're much more critical of sci-fi, because we feel comfortable judging sci-fi settings. In contrast, fantasy is allowed and expected to exhibit arbitrary rules like magic, and to develop romantic stories involving heroes.
If, in a fantasy setting, I'm jumped by rabid fairies from the Underworld, I can buy it. If they cast eternal drowsiness on me and limit my mobility for 10 seconds... OK that's fine. If, in retaliation, I cast a spell to call down meteoric fire from the sky, that's totally believable (not to mention awesome). Fantasy doesn't invite us to call bullshit.
But if, in a sci-fi setting, I'm attacked by robots, well OK that's plausible. Maybe they're programmed to attack outsiders, I can buy that. They hit me with their laser guns... OK, I can buy that that's possible in the future with advances in battery technology. And I guess I didn't get cut in half because I was wearing special nano-armor that, ummm, absorbs laser light. But in retaliation I cast my hacker-spell and... wait... I smell bullshit.
It's easier as an author to just cut yourself loose from present-day reality. It's far more challenging to write in a future-of-now setting, and deal with the annoyances of the real world's rules and history.