I've always considered the 21A just by it's design either an "Ear, Nose and Throat" gun or a "Get The "F" Off Me" gun and a Backup to a Backup.
It's not a Forage Gun nor some Post Apocalypse Wet Dream Assassins Pistol.
It's for a bad breath distances shoot the eye, ear canal, temple and neck up under the chin. Or solar plexus, groin or taint.
Might be debatable if a 3"-5" blade is more useful.
Or one of the Folt's Mini knives or the SPEW that CRKT makes. Or some combination of them.
It has it's place even if it's a very miniscule one.
Melvin always struck me as one who'd show up at a large golf course to play with only a putter in hand.