The range of motion of the disc caliper is very small compared to a rim brake as are the range of motion of the levers themselves. This is what causes me to feel a lack of modulation, it takes very little movement on the disc brake lever to generate a lot of force.
This is what I was really inquiring about with my question. Same reason I can't make a 2 foot putt in golf. It requires a delicate touch and some fine motor skills in the muscles controlling that movement. That could be an issue for some including myself. Big learning adjustment. I can control that somewhat with how much of a gap I have between the pad and whatever it contacts with.