Today is April 20, a day of celebration for marijuana enthusiasts everywhere. But did you ever wonder how it came to be?It's 1971 in Northern California, and a bunch of kids at San Rafael High School are on the hunt for a vast treasure: a secret patch of marijuana plants hidden in the backcountry of nearby Point Reyes.Chinese organized crime has come to dominate the illegal marijuana trade across the country.See, an older guy they know has been growing it, but now he's worried that he's going to get busted. So he tells the kids they can harvest it all and keep it — free of charge. He even draws them a map.Every day after classes, they meet at the statue of Louis Pasteur to continue the search — always around 4:20 p.m. They begin using this as code to talk about the project. First "Louie 420," later shortened to just "420."One of the kids has an older brother who is friends with Grateful Dead bassist Phil Lesh. They all start hanging out with the band, and "420" catches on as a sort of all-purpose slang for stoner culture. Later some genius figures out that "420" looks like the date 4/20, i.e. April 20, and here we are.Oh, and those kids never did find the magical weed farm. And 55 years later, I think I know why. Ready to have your mind blown?There was no marijuana crop. The guy just thought it was funny to send some dumb high-schoolers on a wild goose chase — complete with a corny treasure map. He and his buddies probably laughed about it once, then forgot about it. Meanwhile, these scrubs are combing through the poison oak in search of their dank El Dorado for weeks.So when you think about it, 420 is a monument to how gullible and dumb smoking weed makes you.Also, I've just been informed that today is April 23. Sorry. Ever since they legalized weed out here in California, you can't roll down your car window without being forced to inhale some sickly sweet cannabis vapors. Everyone in Los Angeles has caught a secondhand high, whether they want to or not.That's why I don't know what day it is, and that's why it just took me three hours — as well as two "Columbo" episodes and a bag of Funyuns — to write the preceding paragraphs.Here are some other reasons legalization was a bad idea.1. This isn’t your parents’ marijuanaSorry, libertarians, but the whole legalization debate was built on a product that barely exists any more. In the 1970s, levels of THC (the chemical that makes you enjoy jazz music) hovered around 2%-3%. Today, it’s routine to find 15% to 20% THC in your classic "flower" — that green stuff Cheech and Chong smoked.And nowadays we have a whole new lineup of cannabis concentrates, which can contain up to 60% to 80% THC levels. One minute you're trying to make "The Dark Side of the Moon" sync up with "The Wizard of Oz"; the next you're having a vision quest in the Vons frozen food aisle.2. The psychosis link is real — and better established nowWhen it came to pot, former New York Times reporter Alex Berenson was firmly in the "it's just a plant" camp — where any suggestion that marijuana could trigger serious mental health issues was treated as laughable "reefer madness" scare tactics.Until his wife, at the time a senior psychiatrist at a facility for the criminally mentally ill, made an offhand comment about the latest violent offender she was treating: “Of course he’d been smoking pot his whole life.”Of course?That was the moment that sent Berenson digging, ultimately leading to his 2019 book, "Tell Your Children."What he found wasn’t a fringe theory, but something closer to a quiet consensus inside psychiatry, supported by study after study: Heavy cannabis use is linked to psychosis, and the link gets stronger with potency and frequency.None of this means marijuana will cause psychosis in most users. But the fact remains that legalization normalized a product that, for a meaningful minority of users, can trigger something serious — and sometimes irreversible.This is a trade-off that rarely makes it into the cultural conversation — and never into the marketing.RELATED: Charlie Kirk urges Trump to reconsider reclassifying marijuana: 'Protect public spaces for kids' White House photo3. Legalization didn't replace the black marketOne of the simplest arguments for legalization was also one of the most intuitive: If you make marijuana legal, the illegal market disappears.But that didn't happen.Take California, the country’s largest legal cannabis market. State analysts and industry observers still estimate the illicit trade to be as large as or larger than the legal one. The reasons aren’t mysterious.Illegal sellers don’t test, tax, or restrict — so they can move faster and sell cheaper. They can also use banned, highly toxic pesticides to maximize crop yields.