I would guess it's in case there's fentanyl mixed with other substances, there have been instances of people doing cocaine, ketamine, and other substances, dying from opioid overdose. I volunteer with harm reduction services and many of us carry naloxone, and we advocate for drug testing with fentanyl testing kits, pill testing, and educating people on reagent testing. Unfortunately we can't actually sell or administer these tests at festivals.
Narcan/Naloxone won't help drink spiking, that's usually done with other substances as far as I'm aware.
The RAVE act was passed in 2003 (introduced by Joe Biden funnily enough) and made venues / event organizers liable "for knowingly leasing, renting, using, or profiting from a space where illicit drugs are being stored, manufactured, distributed, or used." with up to a $250,000 fine or "2 times the gross receipts, either known or estimated, that were derived from each violation that is attributable to the person", whichever is greater.
So providing drug testing kits or providing a drug testing station in any official capacity would put the venue / festival officially on the hook for a potentially obscene amount of money because of that pesky darn "knowingly".
Given the current state of the opioid epidemic, I honestly can't understand how this draconian piece of legislation is still law. It is the exact opposite of harm reduction and literally kills people.
Did some digging - it was killed in 2002 but "Biden reincarnated the legislation (now called the Illicit Drug Anti-Proliferation Act) and inserted it into the Prosecutorial Remedies and Other Tools to End the Exploitation of Children Today (PROTECT) Act -- the home of feel-good laws like the measure creating a national Amber Alert system. President George W. Bush signed the PROTECT Act into law on April 30."
Nothing more classic than government overreach sneaking into legislation marketed as protecting kids.
Narcan/Naloxone won't help drink spiking, that's usually done with other substances as far as I'm aware.