My fanon: When you are wealthy and 1/3 Earth Pony, sometime you gotta splurge a little on something completely silly. Like inviting a common Duck to join the royal menagerie just so you can take the occasional soap-free bath with a real Duck instead of a rubber one.
Well, if I didn’t think you, or rather your better mirror, would do that I wouldn’t have said you/she would do that, now would I?
who’s to say i didn’t do exactly that eh heh