Why does everyone? A bad idea out of a need for optical rangefinding. The mil dot method is way too complicated but has served the US forces for so long that has become standard.
Mechanically, there was little reasons to change the way scopes adjusted SO you have the unhappy marriage of MOA and mils.
Yes, there is a movement to a MOA reticle. Several manufacuters now offer that. Mostly from Europe surprisingly enough.
At some point, I hope someone looks through a PSOP Russian tactical scope and really thinks hard about it. The Isrealis have something similar in their Nimrod scopes. Although a bit busy, the MP8 from IOR may just be the height of this design.
A choke style range finder with reticle marks which coincide with drop (just like the Burris Ballistic plex). Range with the choke style range finder, find the necessary line or adjust the BDC/turrent accordingly, engage target. No calculator or fancy spreadsheets required.
For those who are skeptical about that reticles affectiveness, just ask the Germans in WWII, Americans in Vietnam, and Afghans who spent some time at the receiving end of those scoped rifles.
Simplify...
Jerry