I strongly disagree with that common practice. I know the vets have good intentions but what about the mental heath of the puppy? It will for sure be affected by the poor socialization at early age. And really the chance of catching Parvo or other virus is low if you avoid parks and other pets/animals.
Yorkie puppies are really small and easy to carry in a purse, take him out with you so he'll get use to peoples and noises in a safe way. Start with short trip of coarse not a full afternoon of shopping.
When you have friends/family over, give them the puppy's favorites toys or treats to encourage the pup to go to them by himself.
Take your puppy with you to friend/family house that don't have pet. Avoid carpet area...
Discourage people from petting the puppy directly on the top of his head and back as it is a gesture of dominance. The Face and the side of the dog will be way less threatening and help him accept stranger easier.
Good luck and have fun with your puppy.
