Think "sad" is a bit extreme, you could argue that people who buy bling for under their bonnet are sad too then, these can cost £00 and £000 but know one sees it at all....unless your bonnets fell off or the car is at a show. Just my 2p's worth.
A plate you can keep for the rest of your life and it fits on every car. Don't think it's an age thing or a persona thing... just one of life's many choices. A little story, my father in law is a taxi driver and has a taxi related number plate. Punters love it and it sure as hell beats "are you busy tonight then".