A puppy mill is an establishment that breeds puppies for sale, typically on an intensive basis and in conditions regarded as inhumane.
Animals in mills are housed improperly.
Puppy mills are still around because all of the pet stores buy their puppies which keeps them in business. When you buy a puppy from a puppy mill you have no idea if it came from a puppy mill or not; most likely it did.
crowded as many can fit into one crate to just make space for more and more dogs/puppies.
It is harder said than done getting rid of the puppy mills; they have to send in undercover cops, etc, in order to get photos for proof to get a search warrant to take the mill down. But there are millions of puppy mills, some unknown.
Dogs are not treated properly, some starving to death, some left to die, others terribly injured.
There are new improvements in ending puppy mills every day including new technology to help catch the mills, informing the people so they know the extent of what puppy mills do, and people stop buying from pet stores which are helping pay puppy mills to stay up and running.
Dogs living in cages, having to walk over other deceased (dead) dogs.
Puppy Hell, 1/23/17. http://moderndogmagazine.com/articles/puppy-hell-horrors-puppy-mills/269