It’s not just the learning curve that could add stress for workers, but the actual process itself. The whole point of a drive-thru is to order ahead of time and have your drink ready when you get to the window. But with Starbucks’ new policy, customers with a reusable cup won’t have their drink poured until they get to the window, potentially adding wait time to a service model that relies on efficiency. Employees will also have to check personal cups for cleanliness before pouring drinks. Workers can’t sanitize the cups themselves, per the policy, so they’ll have to assess whether the cup is clean enough to use—if it’s not, they’ll pour your drink into a single-use cup.