They're also friendlier for the environment, since they don't have to be mined.
They're also better than natural diamonds, having better color and fewer flaws.
I've heard of people having pets cremated, and having some of the carbon made into diamonds. These diamonds are priced by the carat.
I can imagine a person with a diamond-studded piece of jewelry, with each gem named after a deceased pet, for a very good reason...