Lich Lord of Unx started rising once Innistrad was spoiled, and it kept going up as the Zombie tribe pulled into the casual spotlight
You have to get rid of a second card to pay the cost, but the tempo gain and protection offered in that exchange are much greater than the loss suffered by pitching some other blue or green card
Costing just one white and one generic mana, it can easily be splashed into a deck of any color combination
May have flaws such as tears, pen marks or highlighting, large creases, stains, marks, etc
As a personal example, when I was creating the tests for Judge Academy, I wrote up multiple scenarios with a "right" answer that judges should know, but then couldn't find a rule that backed up that answer