It is banned to lower the number of available mana-positive rocks in the first few turns, and in doing so decrease the frequency of extremely fast starts
I myself do not really see the attraction, 10/10 is threatening but not actually that dangerous
Dragons get access to their own suite of support cards, including some excellent ramp options with Orb of Dragonkind, Sarkhan, Fireblood, and Dragonspeaker Shaman
Not only that, but on turn four or five you can have access to up to ten mana, letting you rocket ahead of your opponents
Let's say your deck features a lot of cheap creatures with prowess and a lot of tempo-based spells like Force Away and Crippling Chill to help you keep attacking
In exchange, you can tap Time Vault to take an extra turn