It's because there are breeders who breed small dogs, not breeding to the stand of 5 to 7 lb. They use the terms teacup to get 2.000 to 10.000 for a pup they deemed a teacup. They usually don't breed like the breeders I've seen here- don't know the dogs health histories, they're MOSTLY wanting to just make a ton of money off the tiny ones.
With that said...
<--- not snarky, but this whole thing makes me smile because I was going to make a little teapot club, but never got around to it. (yet) It was going to be for any dogs under 5 lbs, but that excluded many people, so I was going to make it for 7 lbs and under. I still want to make it, I just haven't yet. Last time I tried the groups were totally messed up, so I'll try again, or help someone else that wants to make it.
The little teapot club was going to have to say in Gen chat that we "do not support unethical breeding of yorkies for lower than the standard of 5 lbs." if they joined. And then say something about why your pup should be in the group. Like the TEAPOTs do when they join, just something fun to do.
It was explained to me also that the Teapots came about because they are so large no one thought they were yorkies. That's a bit of the why's that I know.