I think it just boils down to marketing. Most casual audiences are familiar with TOS more than any other Trek series. ENT was an attempt to recapture the "magic" of TOS and the new movie is an attempt to relaunch the franchise into the mainstream by going back to familiar characters and putting a new spin on 'em, IMO.
But we're also in the age of "prequelitis" and "rebootisis" in Hollywood too...
But we're also in the age of "prequelitis" and "rebootisis" in Hollywood too...