He is given a dangerous task, which requires him to not only traverse the Grid, but also the real world
Higher-rarity cards tend to be splashier, more complex, or more powerful because Wizards uses rarity to help manage Limited formats and card complexity
The sacrifice mode prevents your opponents from playing efficiently (which becomes more useful the higher the power level of your pod is), and lets you recur this card with the likes of Sun Titan
Chandra, Bold Pyromancer Chandra, Bold Pyromancer, like all other Planeswalker deck planeswalkers, is just unplayable
The fact that it provides a sought after role is really what makes it such an oppressively often seen card
That means that if we bounce it, we can't just play it again--it costs a land drop , and we only get one of those, which was already used on Tropical Island