The great stray debate........?

Why do we feel such a responsibility for strays in our neighborhood? I have this beautiful orange boy that comes to my back door for food (which I of course give him) and I just made an appointment (well with a TNR program) to take him in and get him fixed. Why do I feel such a sense of responsibility for him? He's not my cat, I haven't even given him a proper name, but yet I feed him and care for him. He's not my cat, and I don't plan on adopting him (he snarls at Dexter when he perches up on the window). But yet, most of us cat lovers still feel like its our job to care for them. How did we get to this point? And does it make anyone else angry that it feels put on us, even tho we chose it? I could let him wander, hungry, dirty, unfixed, but I just can't. Ugh. I wish people would just neuter and spay and save these poor cats the heartache of being alone. Am I alone in this?