I play MMOs to min/max, to test new strategies, be all I can be, etc. I approach my MMO play the same way an athlete approaches a sport - how can I be better? Do it faster? Hit harder? What stats, for example, are more impactful to my DPS? What the hell even is my DPS? Enter the Parser.

They can also show:
-if people aren't pulling their weight
-if the tank/healer is a dolt
-if there are inherent balance issues with the classes as they are now

This type of program exists in every MMO I've played yet. And I'm pretty sure its technically illegal in those games too - but no one really cares.