Wanted to say the same... It's in a similar vein to how long expertsexchange remained in search results after stackoverflow sites took hold. I usually try to click the MDN links in search results without clicking the w3schools links on accident.
Though lately, caniuse, node.green and similar seem to be my bigger searches. It's hard to keep up with some of the cross supported JS features. MDN helps a lot with syntax/usage, and it's way better than any alternatives I've seen as a pure JS resource. I do wish they'd expand the browser versions supported beyond just which browsers are supported a bit more though, then they'd be my first for almost everything.