I'm sure I read about how it's basically bigging up their ego. :lol: They've got this whole complicated system where you must be ALLOWED to 'groom'/give a nose rub, and in being allowed you're meant to be very complimented. It keeps their self-esteem up or something... I printed a whole bunch of stuff off this amusing, but very informative, website once! Really need to find that link to send to a friend of mine. :lol:
But I imagine it must feel good, too. One of mine is moulting all along his nose, and he loves it when I pluck the loose fur free. ^^ Get lots of happy tooth-purring if I get it just right, or a melty bunny.