What you're not factoring in is that a lich that has no cabal responsibilities is much, much harder to kill than a lich that has cabal powers. Even Emperor cabal powers, which are the king of the cabal power world.

A caballed lich is an extremely hard enemy to deal with, but they're still an enemy you deal with.

An uncaballed lich is where unique gear can go for a long time without being seen by most of the game.