Soap box time!! -- I walk dogs at a local shelter. There is not a common breed that doesn't find it's way through our doors at some point during the year. Sure, you might not end up with a "certified" purebred that's going to win a dog show (do you really want one of those for your family anyway?), but with almost certainty, I can guarantee that you can find what you're looking for at a local shelter. There is almost…
I agree, if we're talking about puppies. There's no reason to buy a puppy. But an adult dog? I adopted an adult dog from a shelter, and I will never do so again.
I realize that the rescue community does its best with the animals, but as an owner of a shelter dog, I really wish somebody had explained to me that the dog you see in the shelter might not actually be the same dog once you take her home. In the course of a few weeks after I adopted her, my laid back, amiable companion had turned into a hyperactive, sometimes-fearful, sometimes-aggressive terror.
My point is that with an adult rescue dog, you are not getting only a dog. You are getting a dog and all of its history. For instance, my dog has a deep fear of manhole covers, tall grass, and a dozen other things. I have no idea why she's afraid, and I never will, because I wasn't there when whatever triggered that fear happened. She's also absolutely terrified of firearms. If I even touch a firearm around her (I've never discharged one around her), she runs away whimpering. I have to preemptively crate her on range days, just to get my guns to the car.
I've been working with her for 2 years, and she's slowly gotten better with some things, but even now she's still afraid of a lot of the same things. And there is absolutely no way I can trust her around children. When my fiance and I get married and want to start having kids, I don't know what will become of her.
All of this to say, I completely understand peoples' hesitancy to adopt an adult dog from a shelter. You can't be sure what you're getting, and while neither can you be sure of what you're getting (in terms of temperament) when you adopt a puppy, at least with a puppy you know that no other messed up human has done bad things to your dog.
Edit: to clarify that I haven't shot my dog...