If I were an evil engineer I’d make retractable benches built into the walls that cost money to pull out. If I were a public official I’d have a subscription package for $60/yr that lets you use all the benches in the city. Must have a valid drivers license to purchase.
I would let anyone extend the bench but if the systems detects the user doesn't have a valid subscription it folds back into the wall compressing the person into a chunky soup.
I would name these benches after our favorite economic model - the meat grinder.