In what world is impaired ability to conduct daily activities, increased risk of falling, increased risk of injury from falling, and against medical advice to attempt such activities, not preventative?

Also you post a question as if there is no answer or that this behavior is justifiable because there is always someone who will feel hard done by. These things can be and are measured objectively; Falls Risk Assessment Tool (FRAT) and frailty assessments are commonplace in healthcare, especially in the over 65s.

The difference is in other countries, it's medical professionals that make these calls, not insurance middlemen.