I understand what you are saying but it seems you have discounted physical conditions that may allow a "mature" individual to safely operate an aircraft but have mobility problems. Let's face it......getting into and
out of RVs, especially taildragger tip-ups can be challenging for some folks who otherwise make it through their daily routines. The taildragger tip-ups require upper body and leg strength since there is no grab bar to assist getting out of the seat and feet moved under the body. I recently installed an armrest between the seats as a prop for egress due to advancement of joint issues in shoulders and knees.....and less upper body strength. Could my condition be improved with a rigorous regime of exercise and diet? Possibly, but that wouldn't stop the calendar pages from continuing to flip.
I am blessed to be in fairly good condition for my age, active (two brisk miles five days a week), able to do pretty much whatever I wish and not obese. But getting out of my RV-6 is a different challenge than it was 25 years ago when I started flying it. Some prospective RVers are dealing with physical limitations that can't be overcome by lifestyle routines and these individuals have to consider ease of entry and egress now and in years to come. For them an RV that doesn't have doors may not be a practical choice.
P.S. I step on the seat going both ways and allow passengers to do the same.