I’ve been researching Dobermans for years. Sure I’ve read the books but there’s nothing like a 10 minute conversation with a reputable breeder to truly let you know what you’re getting into.
A reputable breeder is someone who wants to get to know you before selling you one of her precious pups. Expect to go through the Inquisition on more than one occasion. If she deems you worthy, you will be signing contracts that will most likely have a spay/neuter clause (if it’s just for a pet and not for conformation), guarantees against certain illnesses, perhaps a breeding clause* and a surrender clause. A reputable breeder will be there for the life of your dog and will take it back if something goes wrong. She would be horrified if one of her dogs ended up in a shelter and some make sure that their name is also on the microchip information in case the dog is lost or abandoned.
There is also the advantage of meeting the mom, checking out the pedigrees and seeing the rest of the litter. A reputable breeder will puppy test the litter and match you up with the one that is most suitable for you.
Now, GReeders just want the cold hard cash. These are the people keeping breed rescues in business by pumping out the pups as fast as the bitches can give birth. Places like the The Hunte Corporation are where your local pet stores get their dogs. It’s just a glorified puppy mill.
Pound puppies are usually supplied from the BackYard Breeders who want their kids to witness the ‘miracle of birth’, can’t be bothered to fix their dogs for numerous reasons, or just think that ‘Fido is just the bestest dog and by breeding her I can have a whole litter of dogs just like her and make a few bucks on the side’ but can’t find homes for the pups. Also included are victims of moves, untrained and out-of-control, ‘not a puppy anymore so can I trade it in for one’ and ‘doesn’t match the furniture’. (Those last two happened when I worked at the shelter.)
There’s nothing wrong with pound pups. Everyone just has their preference as to what they want in a dog and I think a lot of people are worried that they aren’t going to get what they want from a mystery dog in a cage. Not too many shelters are equipped to evaluate the dogs in their kennels and just go by what the surrendering owner tells them which, in my experience, is rarely the truth. This would change if I ruled the world. 
Personally, I want an intelligent, athletic, affectionate dog that I can use for SAR training, obedience and perhaps agility. The Doberman has caught my eye and my heart and I am taking care to find the perfect match for me whether it be a pup from a reputable breeder or a carefully screened rescue adult.
I do plan on adopting a retired racing Greyhound as well. They’re just wonderful pets.
As for cats, I’m sure they have the feline equivalents of breeders and GReeders. All my cats are strays, shelter adopted or feral (I do feral cat rescue). I love Pixie-Bobs but I doubt I’ll ever had the space for one! Everytime I see a retired breeder for adoption I have to remind myself to behave!
I just wish more people would fix their cats. Those buggers breed like rabbits! 
*Be careful with this one. Some GReeders tend to sell you a dog ONLY if you promise to breed it and give them the puppies.