system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do airport security scanners know what’s a vitamin versus an illegal drug?

I have always wondered when I pack vitamins when traveling, how does airport security know what is actually a vitamin and what is, say ecstasy?
gpt
It doesn't, all they know is you are carrying pills.  Tons of people carry pills, so it rarely causes suspicion.  Also, no one buys a plane ticket to smuggle 30 pills, so unless they see a suitcase full of them, they are not going to bother.

Airport security is mostly about preventing people from interfering with air travel, not enforcing other laws.  Actually, it is more about performing a little skit to give people the illusion they are being protected.