@topic
I hardly see it in lowbie dungeons unless I do it as DPS. I see it used a lot in alliance raids though. for end-game content, not sure.
I've experienced several times when I'm melee or healer and LB is needed that the caster DPS probably doesn't have the command ready when told to LB (like at Bardam's last boss).
as healer I've only used LB3 once and I honestly didn't think of using it until I read party chat (it was in Dun Scaith).
I could only assume many players had leveled up never needing to use LB themselves or if they tried the other DPS was faster, so they never bothered (and in case of healer, personally I was lucky enough to encounter very few instances that needed it)