Why do dense bodies attract?

Because they neutralize the gravity field.   Light weight gas wants to travel at right angles  to the gravity field.  The negative gradient of the gravity fields will not pass through the dense bodies, so they get layered with a positive phase balance, like a magnetic field curving vertical to the gravity field.  Dense bodies become phase balanced with this counter acting field. The denser the body the more they are phase balanced. And we know that kinetic energy follows the path of minimum phase, so dense bodies in a gravity field become Pauli points for other dense bodies.  The equation ends up the same, but Newton defined it relative to an inertial frame and got the variables a bit mixed. The gravity field is altered, its 'standing' wave concentrates to the dense balance points.

How  do gas clouds become dense? We hardly know that, but I have some ideas. But gas moves at right angles to the gravity field. After the sun burst into fusion, the mostly likely scenario is that it was held together by strong magnetic. Then came the density of planets and sun, much later.