> why can't you just claim that this is just funny money with no real world value, and it has no more seriousness than an in game gold/xp?

That might work in a jurisdiction where the trade in cryptocurrency is illegal but its possession is allowed, but I can't imagine a US or European court would take that argument seriously when crypto has a demonstrable market value. The court would almost certainly treat crypto like a commodity in that case. Wheat doesn't have KYC requirements, but if you knowingly and demonstrably facilitate wheat trades on behalf of a sanctioned entity, you can expect some legal trouble.