The reason is that multicolor boardwipes dip into several different color wheels allowing for a large degree of variety when choosing your boardwipes
That said, if there was one card I think will see the most play outside of the 40k decks, its The Golden Throne
Players receive one mana per land card they tap, and the mana only lasts for that turn, although players can tap the same land cards for more mana in subsequent turns
At the beginning of each end step, create X 1/1 black Rat creature tokens with "This token gets +1/+1 for each other Rat you control," where X is the number of creatures that were exiled under your opponents' control this turn
Several cards appear with multiple treatments, letting you collect the set in any way you please
Gimli of the Glittering Caves will naturally grow over the course of the game, and double strike allows it to make up to two Treasure tokens when dealing damage to a player