They buy them because they want to play the game without taking out a second mortgage or babying a deck like it is made of porcelain
You can get around this by running plenty of free instant speed sacrifice effects, which is pretty easy since black is loaded to the brim with these types of effects
Given this lets you sac Zombie tokens instead of a real creature, its very easy to feed, say, a bundle of decayed tokens to this spell and suddenly find yourself with a winning combo on board
Reds entry, Season of the Bold, does a number of very red things
3 Mirrorform Mirrorform is a six-cost blue instant that can be absolutely devastating if you have the right board set up
Emeria Shepherd works fantastically alongside other angels that can give it indestructible, like Avacyn, Angel of Hope