Quite a lot of cars have rear disks for no other reason than the public perception. For a light car, you'll never get rear drums overheated, other than on a race track in a race situation. Even then, it takes a bit of doing.
But these days, the marketing boys and girls see rear drums as a sign of a not so good car, and rear discs as a plus point. Bit like electric handbrakes - a solution searching for a problem.
