If you weren't on an aircraft and had to jump up, reach over, twist and remove a 45 pound object (the emergency exit door) and move it aside and then get yourself out of the way, all unassisted, would you attempt that without having someone or something (a cane) to balance you?

That's the evaluation the crew faces. They aren't MD's and ties have to go to passenger safety.

Sure, many people can disguise an impairment and make it into an exit row. But, that endangers themselves and others. While emergencies are mercifully few and far between, when they happen, impediments to emergency procedures can be fatal.