In effect, all DM creatures have attack-flying (think Canopy Cover or Elven Riders ) and only the Light, Water and Darkness creatures (and only some of them) have defense-flying (reach, I suppose)
While it is one of the most powerful cards in Commander, WotC decided it is ubiquitous enough that restricting it would be impractical
Its rise seems partly down to its prominence (It was reprinted several times in nearly consecutive MTG sets.) partly due to its simplicity and low strength (It's a fine card in Limited but a straight upgrade, Carnage Tyrant, came out in the very set it made its debut.) and partly due to its big, grinning dinosaur head
So, gather up your friends, take another look through the Card Image Gallery, make sure you're preregistered at your local store, and get ready to come out to the Prerelease and have fun