I have a few Pis around the house, but likewise, the primary use-case that has stuck has been as an Airplay target (using shairport-sync). I'm not using a RPi specific DAC, but rather a cheap USB DAC. I have two of these around the house and haven't had to touch them for years.

The second use-case I have is as an Octopi server to run my 3D printer. I have found this interface to be significantly more user friendly than uploading new designs to an SD card.