There are tons of folks who enjoy these cards, and they are classic and iconic
Being able to deal with Tarmogoyf for one mana (the previous best answer was Liliana of the Veils second ability or a Ulcerate) was a revolution for the modern format
Well, then you could easily kill any number of players
There are some comments below, just not for every card
This means you're free to go all-out on your turn, attack and tap every creature and bit of land you have, safe in the knowledge a few minutes later you'll reset and have all those resources available for casting instants and blocking
They weren't as prevelant as cards from previous cycles, but Witherbloom Command has shown up in competitive settings, and Prismari Command does a fine impression of Kolaghan's Command