I think most of their decisions when making the game stem from what they observed 'other' MMOs problems are. In 'other' MMOs people can misuse parsers/meters a judge a player. I believe it's things that this that SE are trying to combat. It's the same with the ilevel info. They didn't have an average item level at launch because they probably didn't want to create another 'gearscore' type situation. It seems in the end they realised their folly and implemented on in 2.1. Perhaps they could allow you to parse only your own details. If I was a damage dealer i'd like to know if I've improved or not and not just rely on a feeling.

TL;DR: parsers are good but can/will be misused. SE should leave it to the community.