Good choice, as there would be no point - wasted energy in booking, fingerprinting, lawyering, etc.
At least if the arrest record is public the miscreants could be identified.
#4. Just booking those who possessed or whose fingerprints were on deadly weapons can provide a wealth of intelligence information about the thugs, sometimes where they got their supplies, sales receipts, credit cards, license plates, etc.
Even if the charges are dropped and some legal papers destroyed, you know damned well this information has gone to every relevant federal and state (and trusted local) police agencies in the countries.
You’d be surprised how much Intel that was supposed to be destroyed on orders of Leftist Judges in the 70’s, and even now, still exists, “somewhere, in some place, with someone”.