I really don't see the need for them as I'm also not 100% sure what they do exactly.

I get that it keeps track of combat data to show the numbers that are being dealt and healed but with the exception of the first clearers that are the source of all the enrage timer and phase percentage data, to me as long as mechanics are being followed and DPS/Heal Checks are being met I really don't care who's out put is what as everything else is just speed and bragging rights after that.

Example, I was actually berated shortly (Though a snappy comeback quieted it for the rest of the run) because my "Dps was low" by the parser info. Well yea, it's low. I was i180 in a i90 dungeon I can literally half ass it and still meet dps checks. Or the Warrior in The Great Library who could "crit for 7k damage" but couldn't hold hate or survive even small trash pulls.

It seems that parsers provide good "Fun Fact" info or keep track of decent raid data but over all for the casual and mid core player base are kind of a moot point.

I can tell when my DPS is low just by Eye Balling the HP gauges. Because if me attacking isn't making it drop noticeably faster than if I'm not attacking I'm doing something wrong.