Players use creatures, spells, enchantments, and other types of cards to lower their opponents life total and defend themselves from attack
Having the ability to exile cards from an opponent's library, and then cast those cards for free on a later turn can be an easy way to completely shut down an opponent's deck
Sarumans Trickery This card is actually tied for the highest win-rate uncommon (Fear, Fire, Foes
The massive card flow that people want for free in Commander and multiplayer lead them to attack each other, but not you, especially since they don't have to spend a card to get the card draw, so for them, this is free card advantage over time for each foe that attacks each other, and you'll draw more than the card it took to cast him in one or two turns
The most hyped one is, of course, the blue one in the cycle