Why do DPS not use Limit Break anymore?

[Canadane]

When a caster dps I prefer to use my LB on a large pull of trash mobs personally. I always use it if a melee doesn't use it on the boss.

As a tank main, this is generally my preferred use of the LB.
If I see our LB unused and the last boss hits 5% I'm usually just going to use Mighty Guard at that point. I may as well use it since a DPS would do more damage by pressing their rotation that they would by overkilling the boss with an LB.