Short answer: yes
Longer answer: It's a dip in personal dps so that's one reason as to why peeps don't want to do it. Another is for melee's they have their rotations especially if its a mnk or drg. To stop in the middle of it could end up dropping their Greased lightning or Blood of the dragon resulting in even less dps than not doing the lb in the first place. It's less of an issue for sams and nins but it still screws up your rotations. This gets even more annoying as you try to line up your buffs and rotaion to weave a LB in while also doing boss aoe rotations. Additionally, unless you plan on getting another 2 bars you might as well save it for a kill or wipe rather than doing it with the boss at 20% hp.