As one of the confirmed IRs, it brings extra collector appeal beyond the Mega Evolution theme
For these cards, I want the experience of having them laid out in a binder format and seeing set continuity as well as ease of use
For example, an ability that triggers whenever you sacrifice a creature triggers only once
Not quite the traditional Fling effect (here your opponent can remove the sacrificed creature in response to casting the spell), but it has upsides in that the creature itself deals damage to the target, so deathtouch or lifelink will work (as will abilities that trigger when the creature deals the damage)
Otherwise, you could conceivably KO anything out there while surviving most hits in return
This keyword ability is as old as Magic: the Gathering, first appearing in the Alpha set, and is seen on more than 800 creatures that have trample or grant it in some form