A few possible reasons of the top of my head: * Not every renter has a US license or ID * Want to add another driver * The gate security clerk isn’t always a

A few possible reasons of the top of my head: * Not every renter has a US license or ID * Want to add another driver * The gate security clerk isn’t always an employee of the rental company (one exit, multiple companies) * Travelers are tired/frustrated and would prefer to talk to a human to make sure it’s done right * Not everyone arrives with a working smartphone and email or app, or perhaps they just don’t like or can’t use apps * Flight cancelled/missed/delayed and just need to rent a car on the spot