I would say that is why most people who don't want it are so opposed to it. Deep down inside they know they are bad and have no intention of improving. As long as content is being downed they are content to have someone else carry them along.
Additionally, in the end it will help class balance. If you have a DPS class out DPSing another by a wide margin there is a balance issue. If you have a healing class outhealing others by a wide margin there is a balance issue. If you have a tank class taking more damage than another, once again its a balance issue.
You cannot know any of these circumstances without a damage meter.