By the time you've paid for a drone and someone to fly it in each city, you might as well just pay someone minimum wage to drive around photographing the lots from ground level. It'd probably work out cheaper.
And if you were trying to collect information, you'd be able to get a lot more info from the license plate numbers or the make/models of cars. You could also get information on employment by looking for which cars are parked where, since store employees typically have to park further from the entrance. There's a lot of information that you could get from ground-level that you miss at satellite level.
The real question is - is it worth it?