I don’t watch tv, so I’m not sure, but I don’t think those commercials are talking about animals who are just left alone to roam the streets, I think they are talking about animals who are affirmatively mistreated by their previous owners.
Most domesticated dogs and cats are bred to be pets. There aren’t supposed to be random dogs and cats roaming the streets. They belong in homes with people. For lack of a better term, they aren’t “naturally occurring” animals.