Why are the salads and sauces in hamburgers on top of the patties instead of under them?

An ideal hamburger has two pieces of completely baked bread.

It is brittle from the surface to a certain depth.

The next step in many practices is to butter the bread.

Form an ideal waterproof layer.

The etc theory of "fear of bread sucking sauce" is basically untenable.

So hamburgers with opposite themes or sauces on the top and bottom are very common.

I guess it is:

Due to that gravity of the sauce and the pressure of pie and bread,

The sauce under the hamburger penetrates into the bread more easily.

It doesn't taste that good.

The sauce on the meat pie doesn't penetrate into the bread on it so easily.

Because it is not easy to slip,

When the sauce doesn't go deep into the bread,

If the patty leans slightly on the sauce, the weight may slip off.

If the sauce is on it,

Bread is lighter and less prone to slipping.