Normally, Obscuring Haze is a costly three mana, which is too expensive for a simple fog effect
Four life for each extra card the Library nets you isn't nothing, but - at least early on - it's well worth paying, and can launch you ahead of the competition
Special Resource Points - Some characters have special resource points
Defensive phase-outs like Teferis Protection also allow creatures to dodge boardwipes, edicts and other non-targeted removal, where many flicker effects simply return them to the battlefield in time to perish by the next spell you had been responding to on the stack
Finkels US Nationals winning Napster deck played a full four (detailed here ), but that was the first time you had to play with just Vampiric Tutor for selection (without even the luxury of Demonic Consultation or Demonic Tutor or whatever)
From Aristocrats to Sacrifice there are tons of archetypes this is a must include in