Its usually wise to ensure the creature makes it through, even spending some resources to do so, as the rewards can be game-altering
The Thirteenth Doctor might want a particular kind of Simic deck (say, a cascade one) but at three mana, the untap condition is more than worth it
Not only can Birds of Paradise tap for three mana now, but Time Vault exists
So it has the floor of also being able to Shock planeswalkers
A beast of a card, Chernabog, Evildoer gets cheaper for each character card in your discard pile, so it's easy to start pondering up ways to get him out nice and early and start punishing your opponent
So long as Combat Celebrant hasnt been exerted this turn already, you can exert it, making it so it doesnt untap during your next untap step