Good question. In most places, those ads are not put there randomly by the bin manufacturer. They’re usually part of a street-furniture advertising system. A city or waste authority signs an agreement with an advertising company or a bin-maintenance contractor. The company gets the right to place ad panels on public bins—often in specific zones and formats—and in return it may pay the city a fee, share revenue, or cover the cost of installing, cleaning, repairing, and emptying the bins.
The advertising company then sells that space to brands, local businesses, or public campaigns. Because bins sit at eye level on sidewalks, transit stops, and busy corners, they can offer repeated local exposure at a relatively low cost. Some programs also reserve a share of the panels for municipal messages, recycling reminders, or community notices.
Of course, the details depend on local rules. Cities usually control size, placement, content standards, permits, and sometimes limits on alcohol, gambling, or political ads. Some places avoid bin ads entirely for aesthetic or policy reasons. So when you see one, you’re usually looking at a small public-private arrangement: the city provides the location, the ad company handles the inventory and upkeep, and advertisers pay to reach people passing by.