'I reckon there are plenty of undeserving blue badges when you get down to it. As in most things in life there are probably faults on both sides. Just sayin'.'
An elderly relative of mine (early 80's) maintains two allotments, my garden, and trims my trees using ladders and a chainsaw. He is very proud of how active he is, in comparison to many others of a similar age.
However he has a dodgy ankle which sometimes gives him some pain for which he straps it up and takes some paracetomol. Whilst it is strapped up he can still look after his allotments.
For this he gets a blue badge.
I have a friend in his late 30's who commutes to the city by train every day. He has dodgy knee cartilages which give him some pain. He's got a blue badge too!!