What about students who pay a hundred bucks a month for lessons, and get paired up with the blind person? Now that student has to make concessions to accommodate the blind person. Going a little slower, exhibiting more caution--taking away from the intensity of thier own training. They can't train full on like they could with a regular student.
What is a "regular student" - do you only train with very fit young people who can match your intensity? And what about someone who is much more advanced and fit than you: do you not expect them to account for the fact that you cannot train to their level?
There is value in learning CONTROL of one's speed and intensity of training. Some of us are health care professionals, mental health or rehab or corrections professionals, work w/ disturbed youth: we HAVE to include in our training on the mat a level of control that can do an effective pin or lock on an attacker without causing harm. There is a role for all training.
WAIT. you just posted on another thread that you have chronic back pain so you can't stand to be slapped on the back and that you "don't train in a dojo." So, tell me: how do you know what it is to be a "regular student" or to have your training affected positively or negatively by students either more or less advanced than you?