I know several illustrators who used airbrushes for the majority of their illustration work two decades ago (or more), who now use only digital tools. Many "former airbrush artists" see little reason for anyone to bother with clunky ol' airbrushes that require constant cleaning, maintenance, and replacement parts.
But, there are reasons--good ones!
Just last week, I was asked to repair an arcylic (mostly airbrushed, with some "traditional" brushwork) painting for a fellow artist. She had a 40 x 40 inch painting that had a small tear in the canvas, and she needed it fixed, so the painting could be exhibited.
My first step was to "patch" the tear. I cut a small piece of unprimed canvas (from a scrap piece I keep on-hand for exactly that purpose) and attached the patch to the back of the tear using acrylic matte gel.
Once the patch was dry, I applied gesso into the "tear" from the front, sanding it smooth once it, too, was dry.
Then, using the airbrush, I touched up the "fixed" area, matching colours to the rest of the painting.
Lastly, a bit of "traditional" brushwork, and the repair work was done, and the painting looked like there had never been any damage to it at all.
When you have a project that can't be easily fed through a printer, or when you want to retain an original photograph, document, or painting (rather than ending up with a PhotoShop corrected copy), airbrushing is one good way to go about "fixing" original pieces.
I'm going to be using airbrushes quite a bit in my next several paintings, probably with both acrylics and oils. I need to figure out a good formula for an airbrush oil-paint medium. (I have a few ideas...)