Austen Jux-Chandler, the vocal producer behind records with Adele and SZA, rides the preamp gain to handle vocal takes that swing between quiet verses and loud choruses. He raises or lowers the pre as the singer's level changes, so the compressor in the recording chain always reacts in the same range.
He usually only pulls the artist back from the mic if they want that hot, edge-of-crackle sound from really belting it out. Otherwise they stay put, since a good mic handles more SPL than a voice can push, and the preamp does the leveling.
A stepped gain preamp makes this practical: fixed increments are easy to recall and reset between sections and takes, keeping levels consistent for comping later.