Describing accuracy/consistency in angular measurements such as MOA is by far the most efficient way to describe it since it is independent of range. It just takes less words and less information to convey the value. 1 MOA is often a benchmark for what is a "good" shooting gun, and when you use MOA instead of inches, etc., that benchmark can be applied at any and all ranges, be it 20yds, 1000yds, or anything in between. It creates a constant that can be quickly and easily tracked.
You seem set on 100yds being a de-facto range for shooting/testing guns, but that is not at all the case for me and many other shooters, be it airguns or powder burners, or even some archery equipment. I do tend to sight in many of my PB rifles at 100yds, but across the board, I don't actually shoot at 100yds very often except when sighting in or checking zero. But that doesn't mean that I'm not constantly tracking my groups as I shoot, and I use MOA to do that. Otherwise, the fact that I just shot a 1.5 inch group is meaningless since we don't know if I was shooting at a range of 50yds or 300yds. One of those 1.5 inch groups is quite poor, and the other is outstanding. MOA makes the distinction quite easy.
Once you start using MOA values it will become second nature and you will likely see the benefit. Then you will also see the benefit of using those MOA or Mil values on your scope reticles as well, instead of just seeing them as random hashlines for holds.