There is zero literary evidence from Ancient Greek, Latin, Assyrian or Chinese sources. Meaning: it was a long-standing taboo by then.
https://en.m.wikipedia.org/wiki/Soma_(drink)
https://www.bbc.com/travel/article/20170307-the-intoxicating...
The only explanation that makes sense to me is a massive multicultural taboo against magic mushrooms.
You have to eat fairly substantial amounts (assume 90%ish water, you probably want at least a gram of dry mushroom) of a mushroom that tastes awful, is tiny, upsets your stomach with indigestible matter, and you'd need to eat them in a fairly short window of time. I don't see it as particularly unlikely that we only realised here after getting it from elsewhere, the Norwegian forests have a pretty substantial list of better options.