Buying a pizza and giving a very large tip via bitcoin might be a way to launder money, which is what KYC is supposed to prevent track.
The same could be said of paying in cash, and even more so by paying in cash in a restaurant or picking up food in person without giving out a name or address as you would with home delivery. And yet, no one trys to make you KYC for this.
If someone were to take out a lot of cash from the bank, there are reporting requirements the bank has to follow. If someone were to take out smaller amounts of cash in order to avoid the reporting thresholds, there are other reporting requirements.
From an AML perspective, when selling gift cards for bitcoin, it is very difficult to tell when someone is buying many lower denominated gift cards in order to avoid KYC thresholds.