I know quite a few Seniors that wear them. We have one who earned his as a cadet, and is a 747 pilot who is in the air more than he is not. Since he is not a CAP Pilot he loves to wear his solo badge
Since most solo badges are earned as a cadet, when a senior wears them, it lets all the cadets know they are a "prior service cadet" and they respect that, at least around here anyways. Rock them until you get your aircrew or observer wings.