I'll bet...the carts have some real advantages...go where the business takes you, you don't have to pay rent on a building, you don't pay for electricity, plumbing or sewer (although I imagine that the licenses for those carts are not cheap)
...and the carts are only there a couple hours each day. They're off-loaded from trucks around 5:00 or 5:30 and are gone by 11:00.