We have big box stores for pets.
We have semi trucks burning diesel to bring pet food and pet supplies to all parts of the world.
We devote some amount of farm land and livestock to feeding those pets.
It’s interesting when people suggest to reduce global human population but I have never heard anyone suggest to reduce pet populations as a method for combating climate change or for simply reducing resource usage.
The worldwide dog population is estimated to be 900 million.
There are 600 million to 1 billion cats living in the world today.
I mean, most pets are a luxury but not all, depending on how you define pet.
Many service dogs and emotional support animals are absolutely necessary for physical and mental health, but then you could also define those as not necessarily being “pets” but rather “tools” for healthcare. Anything where the human is not dependent on the animal is definitely a luxury though and not necessary in the slightest.