Other reasons

That I dislike the military. Apparently many soldiers being deployed overseas are just dumping their pets . On some level I can understand how this would be a small issue compared to the fact that these soldiers are going overseas to what might be their own deaths. But, humans domesticated these animals, and we made them unable to survive in the wild. It is our responsibilty to care for them, not put them to sleep because they are inconvenient. It is not their fault that they can no longer hunt and live on their own. We did this to them with careful breeding over thousands of years. How can we now just turn them loose to starve or worse, kill them for what our ancestors did.

Purchasing or adopting an animal means that you are assuming responsibility for that animal until the day it keils over from old age or it is so ill that it cannot be made better. And it infuriates me to no end that some people would be willing to just leave a helpless animal behind when they move because it is too difficult to take them along. And these dogs get surrendered, then spend ages in the shelter until they go cage crazy and have to be put down. Where is the culture of life now?