I mean if you're writing a ray tracer and the reflected light has more intensity than the light sources, then that's not desired. You can have the same sort of thing going on with a fluid simulation.
One of the nice aspects of Stable Fluids is that you don't need to iterate the pressure correction terms to convergence. Just run a fixed number of Jacobi or Gauss-Seidel sweeps and keep performance consistent. The only drawback of this is some mass loss in areas, which for the present purposes is acceptable.
I should add that this is a major "tell" for detecting when an app uses the Stable Fluids method: obvious mass loss (and very viscous, energy-dissipating flow).
Sure, but conservation in ray tracing is also a goal that not everyone has and isn’t required for teaching or games or making pretty & even plausible images. There are plenty of situations in both ray tracing and fluid simulation where conservation is not desirable.
