Maybe the connection is a creature type, or the cards play well together, or they have some story element in common
Collective Brutality The life drain on Collective Brutality might be the least picked mode, often just tagged onto the Duress or -2/-2 so you can discard a reanimation target, but thats a pretty decent effect
So much of the deck features cards that can boost or benefit from cards being facedown under them
Popular cards in this category include: Farseek can find nonbasic lands, like Steam Vents, but cant find Forests, even basic ones
While they may not have won yet , they are assured that it is in their grasp, and sometimes that's all that matters
And theres plenty of other uses, especially in Commander