Run removal
Blood Moon turns all nonbasic lands into basic mountains, so decks that lean on fetches, duals, shocks, and fancy utility lands can suddenly be stuck doing nothing
The mana advantage, more often than not, outweighs the downside, especially when paired with cards like Lotus Petal that can tap for colored mana
Ygra, Eater of All from Bloomburrow changes all that by turning all my creatures into food
The numbers are jacked up to accommodate attacking 40-point life totals, but translate that over to 1v1 20-life formats like Cube, and Bombardier goes off the deep end
Although not all cards are valued at quite that much, it still shows that there is a player-based market involving hundreds of millions (according to reddit, almost 3 billion) dollars worth of cards