The rear seat is all vinyl.
The front seats have leather only on the parts of the seat your body actually touches when you are seated. The sides of the front seats are vinyl (or cloth). The backs of the front seats are vinyl. The headrest is all vinyl. The places, even below your thighs, which do not directly touch your body are all vinyl.
Advantages of the parts which are real leather: warmer in winter, cooler in hot weather, less sticky than vinyl in hot weather.
Now this is certainly silly...but pictured is how the rear seat area of my car currently looks.
I figure, if someone wants to sit there, they can bring their own pillow. And spills are very easy to clean up on metal surfaces.