And entropy is a measure of this degradation. This is a statement of the first and second laws of thermodynamics. And the term laws doesn't mean edicts, but ally statements about how matter behaves. Physics is about how matter behaves, and these are statements about that. This is simply a statement that although the energy in the Universe remains constant, the entropy tends to go up.
Negative entropy is a measure of the usefulness of the energy.
Gravitational energy and the kinetic energy of large moving objects is completely usable. Heat energy is not, because the directions of the motions of the particles have been scrambled. That's what we call heat. And temperature is a measure of the mean kinetic energy of the molecules. When you panic stop on the freeway, the kinetic energy of your large moving vehicle gets scrambled to heat by friction in the brake drums and the brake shoes, the tire and the road.