Mill Though milling and exiling cards isn't the same thing, there are many ways to turn milled cards into exiled ones, which makes devoting a lot of your deck to doing it worth it
Some commanders within the format actively seek to function as key political pieces that can assist you in making deals with opponents
Riot lets you pick whether you want your creatures to come into play with haste, an important mechanic when it comes to pushing damage through, or a +1/+1 counter on them when they enter the battlefield, making them bigger and synergizing with cards like Doubling Season
After all, who needs to build the best deck when you can instead build one that convinces your opponents to fight one another
It seldom grew to that size and, even when it did, it did so late enough that a 6/6 creature without evasion wasn't all that impactful