Any gas presses on a body immersed in it from all sides: from above and below, and from the sides.

Any gas presses on a body immersed in it from all sides: from above and below, and from the sides. Why, then, does a buoyant force, always directed upward, act on a body in a gas?

Because the buoyant force (Archimedean force) is always opposite to the force of gravity and, for example, is impossible under conditions of weightlessness. When there is gravity, the body immersed in a liquid experiences a pressure difference between the lower and upper parts of the body. This pressure difference is manifested as a buoyant force, opposite in the direction of the force of gravity.