Yes a number of us make terrain apps. From your statement I should add that these terrains are not merely random. The initial generation might be but then more algorithms are applied to generate more and more things. Your right in that the real world is so infinitely complex that its impossible to generate them in a computer however I also believe that they are also too complex to be artistically drawn too and that a computer can do a better job of getting closer than a person can - certainly in a given small amount of time anyways.

So we apply algorithms to approximate climate so that mountains are colder and then apply more to simulate frost erosion and also the movement of rock down sides of hills. We do water and glacial erosion too which makes U shaped valleys and rivers cut into them at the bottom. We model vegetation based on climate and a few other factors and try to model the overall look of the terrain and then after all of that we texture them. Usually thats done procedurally so that beaches can have pebbles. My GTS has some parameters about high tide which causes the sea to smooth out those areas and the texturer then shades different types of sand and beach flotsam.

Of the image below not a single factor of it was hand made. The terrain, the flow, veg and texturing is all computer generated and not at all directed manually. It could keep making these endlessly. Your right tho its still not enough to make it look real. It still looks computer generated.