This world has more than plenty of animals to go around. Hundreds more roam the streets, hungry and often ill. A sad fate awaits them without human intervention. And that is the key. People rave about the animal-rights activists and wonder why humans don't come first with them.
Humans do come first.
And it's in the interests of the people who have to administer those lethal injections, who suffer the guilt of driving the car that killed a street dog, that cutting the pet population would benefit most. People in humane societies and animal shelters would like to see nothing more than their jobs to become obsolete. The only way for that to happen is for people to intervene in their behalf by acting to reduce the numbers of new animals spewing into the world. Not really, when you realize that two cats can be the springboard to a population of over 80 million in 10 years. There are no real excuses.