As Dr Danten points out, the pet industry has the same four sectors that every industry has: it is driven by the consumer and made possible by the producer, the servicer, and the disposer. Animal control done by SPCAs, pounds, and others, is the fourth sector, and without it, the other three parts would be severely restricted.
The pet disposal sector is so foul that it has to disguise itself as animal welfare. And it has...very successfully. Pounds now call themselves shelters, and humane societies such as the SPCA are disposal contractors. Not one of them is saying the only thing that can stop the cruelty, and that is to say that it is wrong to own other species. If they did, they would be out of business. So would all the others in the pet service sector, who appear to be acting out of compassion for animals, the vets, trainers, behaviourists, and rescuers. Most are compassionate, but they are prolonging the suffering by participating in the industry and by not understanding that they are part of the problem just as much as the producer, the seller and the disposer.