This way you have other ways to add value to your spells even if your opponents keep Tergrid off the field with removal
Similarly, Vanishing cards like Aven Riftwatcher were introduced in Time Spiral block, which featured Planar Chaos and Future Sight alongside Time Spiral
It see play in 1 formats: Brawl
Also, keep in mind that some of your interaction comes in the form of your morph creatures, but you can morph your creatures at any time, including at instant speed
Brave the Elements can even help your creatures shed auras like Darksteel Mutation or Shiny Impetus or to turn your own board into a wall of defenders that can survive combat when an opponent swings into you to force you to trade creatures or take big damage
The potential to activate it multiple times a turn lets you get really far ahead, and it does all the planeswalker things provides board presence, card advantage, and removal in a single card