The point of legalizing it is that it can be regulated. With legalization comes standardization. You can have legal employers who are legally required to verify employees’ ages, using established systems.

It would also allow the government to confirm that the employees are legally allowed to work in the country. Either citizens or on a valid working visa. This would add substantial roadblocks to trafficking, where one of the primary means of control is moving the victim to another country illegally and then taking their passport away. Limit their mobility, and you limit their ability to flee. But by requiring that all employees are legally allowed to work, it adds a significant roadblock to the traffickers’ MO.

When I was in high school, finding drugs was easier than finding alcohol. Why? Because drug dealers didn’t ask for ID. With alcohol, you had to know someone with a cool older sibling, or know a cashier who would be willing to sell if you slipped them a twenty. But since the latter was under constant surveillance from their employer (because cash registers are almost always video recorded for security purposes) that wasn’t very easy to find. But with drugs, you could walk up to any skater or stoner and ask if they had a connect. You’d have drugs in hand in less than 10 minutes.