Ideally, you can activate an ability of one of your cards that requires you to discard a card
However, if that Land is a Plains, then you actually get to put that nonland permanent back on the battlefield instead
Especially if we're talking about value cards like Decree of Justice that build up your board
Because the decks are balanced against each other, you can sit down with other new players and enjoy a fair and engaging match
While this doesnt spiral out of control quite as fast as a card like Cathars Crusade can, it still plays a solid role in any white deck looking to go wide with small Creatures
It's also hate that doesn't necessarily conflict with some other artifact strategies the way Stony Silence and others might - if a player has more expensive artifacts in their deck, for instance, Meltdown is still a great sideboard card that likely won't destroy their own game pieces but will still affect a cheaper-costed deck