I don't understand your dichotomy between muscle power and brain power, but I can answer this question which is at the heart of your thesis (so far as I can understand it): there are many people who, for whatever reason, do not have the desire to learn the fundamentals of photographic exposure -- they just want to take pictures and don't want to have to "be bothered" by knowing/controlling how the camera works. (See post #15)
Originally Posted by Chan Tran
Another facet is that over the years the metering has become so good that it increases the chance that A-mode will produce a decent exposure. One of these days I'd like to graduate from an archaic center-weighted meter (Nikon F3) to something with a more sophisticated matrix meter.
But if you want to talk muscle and brain power... I can't use modern DSLRs because I don't seem to have either the muscle or brain power to press all of those buttons and scroll through all of those menus. Or maybe I just can't be bothered by trying to control a camera that way.