Combat Celebrant is a bit different
Loxi: I mention opportunity costs a lot, and utility lands in colorless decks tend to have the lowest of those since they don't really have other lands to lean back on besides Wastes
The payoff of transforming to Aang, Master of Elements is massive considering you already drew 5 cards (assuming you drew a card to start your turn)
Aragorn, the Uniter will probably see very little play in booster draft Limited and casual play with its many colors, however, so Commander is its best bet even if this card wasn't actually put in the pre-con Commander decks like Aragorn, King of Gondor was
That said, it's difficult to play it as your mono white commander
Mostly though, they make Hydra spells you cast cost four generic mana less to cast