I came across something earlier that sd the dogs in the terrier group were breed for specific jobs where the toy breeds were more for pets. That toy dogs were traditionally pampered and treasured by aristocracy around the world.
From
Yorkies - Yorkshire Terrier Dog & Puppies :
"Toy Dog Breed Information
Dogs in the Toy Group, which include the Yorkie or Yorkshire Terrier, were initially developed to ease the lifestyle and provide pleasure to rich people. These dogs were initially owned by the wealthy and were viewed by others as status symbols - a luxury item with little apparent purpose. Dogs in other groups had specific working roles and played a major part in providing food for the table and therefore justified the cost of their upkeep and care - these were the dogs which were commonly owned by the lower classes. Changes in the economy, lifestyles, living conditions and the environment brought the luxury and pleasure of owning a toy breed dog, such as the Yorkshire Terrier (Yorkies), to everyone."