My mother is one of these horrible people.
She has a VERY overweight Rat Terrier and she lets his nails get WAY too long. I try and nudge her "Hey! Allie needs to go to the vet for XYZ...whatever, Why not bring Jorge to get his nails done?" It is so sad! I have gone and kidnapped him while she was at work sometimes just so that they didn't get this bad. If you are going to own a dog, care for your dog.
Sorry, don't mean to offend anyone, but this is a personal soap box of mine.