Gourmet food is intended for food snobs. It's purpose is to look nice, and have lots of "depth" that they can talk about with big fancy words. Complex flavor is nice, and far more important than good flavor.

The round burger is horrible.

It is harder to eat, since it can't actually be a sandwich, being too big for the mouth. It's also prevents you from layering things on top of it, since it doesn't have a flat surface to support another layer (or the bun) well.

It's also harder to cook, since it is much thicker, and thus heat takes longer to penetrate it. So the outside is likely to be overdone by the time the inside is properly cooked. It's impossible to properly apply a sauce to (yes, you can cook a sauce into the burger, but that changes the sauce's flavor, the burger's texture, and how well the burger holds together), since the surface area to which you can apply the sauce is far smaller than on a flat patty of similar volume.