Last time Difficult Child lived here with us, he asked me for clippers. His nails were long, dirty, and scraggly, so I gladly got him a new set for himself.
I noticed his nails never got any better.
Later I found out he used it to clean his drug pipe.
Sigh....
However, your son may just be using them to actually clip his nails!
And the image of him turning up his nose at using someone else's 'used' nail clippers just sends me into fits of laughter.
Most of our kids are just mainly tragic.
Your son has his moments of tragic, but also, large doses of haplessness and humor.
I think he will eventually find his way. It just may not be the path you had hoped for him, but he could be OK in his own way.