Conqueror discourages teamfights
Lets say you are Master Yi. You need 6 stacks on rageblade and 4 seconds fighting time before Conqueror kicks in.
Basically there is no way for Yi to get Conqueror stacks for teamfight. It's much easier to split so you can get conqueror stacks rather than go in teamfight and do 0 damage
So that's the reason why some champions like YI would never join teamfight. It's too hard for melee champions to make COnquero Rageblade work in teamfight
On other hand keystones like Dark Harvest encourages to teamfight more often since it does more damage the more souls DH user harvested
So don't expect Conqueror user to teamfight. It's way easier to split and have full power rather than go in teamfight and die while doing nothing