Protect stars during aggressive processing.
Strong stretches and denoise can change star color, halos and shape. Masks keep those decisions controlled.
Star masks make astrophotography processing less destructive.
A star mask helps separate the stars from the rest of the image so you can stretch, denoise, sharpen or reduce stars without damaging everything equally.
Process star and nebula layers differently.
Starless and star-aware workflows make it easier to improve faint nebulosity without bloating stars.
A mask should be adjustable.
Useful masks need control over scale, halos, cores and protection strength, not only a one-click output.