Convex mirrors were not simply decorative?
It's twue. They were called Butler's mirrors, since their traditional use was to permit the butler or wait staff to view the dinner guests and whatever need may arise without rudely gazing upon the upper classes while they dined. My mother was like that. In a restaurant she'd often say - "I can't eat while those people are staring at us!" And we'd have to put everything in a dogie bag and leave. No wonder I'm nuts.
Similarly, convex mirror use around the house became a necessity for the other servants to be able to see into a room or a hall before entering to avoid encountering the master or his family. The downstairs servants especially were an unwelcome sight upstairs.
But of course! It was also an early surveillance system - the guests could be monitored in case they tried to steal the silver ... or the accessories. They are still used commercially today, while domestic use is more decorative than functional.
They can be quite gay when tastefully festooned for the holidays!