Think in my case it has to do with ethics. When I moved to the area I'm in there were several strays abandoned by their owners who moved away, or simply didn't care. Here, animals are considered replaceable with a new one, and would have likely not survived the winter.
When I spoke to locals, they simply shrugged and ignored the feral cats and dogs. The local spca suggested I let them starve, so there would be no kittens or puppies in the spring. A local hunter trapped them, and killed them throughout the winter. This outraged me, that they had trusted humans and then were rejected and destroyed by them. When I discovered this, I made winter shelters and fed them. Also protected them, brought them to vets for shots, rid them of their parasites and found homes for them. This is not the first time I've done this. I adopted some of them as well. I have a total of three cats now. All originally strays.
Have been rescuing animals since I was a child, the idea of a creature injured or sick or hungry is intolerable. My ethical sense seems hard-wired to help those that need aid, especially those that can't do so themselves. In my view animals that are affected by others, then abandoned, are used like objects. This makes me angry, as pets become societal victims and expendable. There is a certain familiarity to it all.