There are people who have very bad ingrow problems when they are shaved, especially if they have had operations before, if you want a "sensible" reason.
My background is in Occupational Therapy. Much of my time has been spent working with older and disabled people helping them to get out of hospital and back home, if this is what they want. You would be shocked (I hope) at the number of well meaning family members, neighbours and medical staff who thought (I am retired now) who thought that my job was either to decide whether or not such and such a person would be allowed to go home or, worse, that my job was to make the person do what the family member/neighbour/ doctor/nurse thought was "best for them" which usually meant a "home" rather than their home.
Please understand that where a relative or neighbour is being ground down by the needs of a person, then part of my job was to facilitate conversations about what it is reasonable to ask a relative or neighbour to do, what isn't and how the gap can be bridged. Sometimes the gap really isn't bridgeable and the person really isn't competent to decide where they want to be but often the objections are because the person doesn't live their life in the way that the objector expects...
which at base is where we are now....a person choosing to live their life (or in this case risk it) and other people expecting that something different is right.
As I said earlier, this is complicated because the young man is so near adulthood which makes me suspect that he has been adjudged not to be Gillick competent, or that the appeal process will last until he is an adult.