The cars may be spread out in reality, but the official operating area (as listed here: http://www.car2go.com/austin/en/file...ating_area.pdf
) is (in Austin terms) very tightly restricted. The area shown barely gets you outside of "downtown" to the north, and only very slightly so to the south.
Austin, like most Texas cities, is a very big, spread out place. The metro area stretches from Round Rock TX to the north, and about ten miles to the south. East, the depth of Austin is not so great, but the western dimension includes a ton of development of which I am only vaguely aware.
The spotting of the cars on the "Operating area map" is probably cars in use, rather than where they are allowed to be dropped when not operating. If drop-offs were not so restricted, you'd have single cars spread out all over creation, with no "concentration" of the parked vehicles where they would be convenient to be picked up by the intended program subscribers.
When we picked up our GPS head unit at smart Center Round Rock, they had a large slug of the cars for the Car2Go program parked in their paddock. It was weird to see so many smarts parked in one place.