When gravity pulls stuff together in space it is often the case that a major mass at the center of gravity results, and also an accretion disk which is a broad circle concentric with the central mass. Satun’s rings are the magnificent example.
Another solution is two equal masses circling each other in the same orbit.
Conservation of angular momentum ensures that the rings cannot merely join the central mass. Components of the rings presumably collide with each other and this is a dissipative process which means that the dynamic energy (kinetic + potential) of the system decreases. (The dynamic energy excludes thermal energy and such. Dynamic energy includes only those Newton would include to compute orbits.) Dynamic energy of the system is thus conserved except that collisions transform dynamic energy into heat. An accretion ring must therefore be temporary.
I have heard that there are arguments that Saturn’s rings are not more than a few million years old. Perhaps some other gradual or intermittent process sustains them.
There is about Saturn very little space junk except for the rings them selves. Such junk is limited to very special orbits thru the gaps in the rings; passing thru the rings proper soon results in a collision. The rings are king of the mountain; join them or die! The Cassini-Huygens orbiter must be careful to miss the rings whose plane it passes thru every few hours.