Well, Krrik, Son of Yawgmoth is a seven mana 2/2 with lifelink that gets a +1/+1 counter on it whenever you cast a Black spell
The main exception is Instants Instants, like Sorceries, represent one-time-use magical spells that go to your graveyard after they take effect
I am not one of those great math guys (I studied technical physics only), but if, for example, Creeping Chill got banned instead of Faithless Looting we would be left with 14 free spells
(So much so that now most of the cheap acceleration we make costs at least two mana.) You can start powering out your threats quicker than your opponent, putting you at a sizable advantage
A card from an early print wave can be more desirable than a later reprint if supply was tight
Spidey is here!" 3/2 With Great Power