Buying a pug, I’d agree because it more directly comes from the breeder. As far as I know there’s no way a breeder or previous owner would know their dog is being adopted unless they’re actually making an effort to check in with the shelter. Even if they choose to, they no longer legally own the dog so that info is confidential. Regardless, they get no money out of sending them to a shelter.

Also dogs that don’t get adopted are often killed making it an ethical choice to adopt.