It's also worth noting that by being free/cheap, or by "just wanting to pay for dog food" you are contributing to the exact problem of why photographers can't make any money.
There are a billion people out there who just are in it for "some folding cash" or "enough for a six pack of beer", or even "I can't charge for my services because I'm not good enough yet."
Guess what? That average $25K salary? Supply and demand. There's a ridiculous supply, so there's relatively little demand.
Many of us here are (or have been) guilty of it. I wanted to make money just to buy gear. Granted, I bought a lot of high-end gear and charged a fair bit to make it to that point, but even at my level... I was contributing to the problem.
I'm really not trying to add to any problems that exist and I understand what you're saying. Maybe the dog food thing was a bad example. The fact of the matter is that I own two working and performance canines and I'm passionate about the things I do with them. Their upkeep, care and activities cost me about 10-15,000/year. I'm also very passionate about my photography. I would love to combine the two into something that is viable and would allow me to continue participating in both.
I photograph my mom's dog for free and I've offered free service to my PSA club because I would really love to add to my portfolio as the breeds in my portfolio are very limited.
That being said, if my club were to host a trial and other clubs from N. America came to compete, my photography would not be free. People would be expected to buy the photo of their dog if they wanted it.
I guess I see it more of a trade off... I'm taking photos of their dogs for free, but they're allowing me to practice on their dogs. So, if I don't get many usable shits, it's okay because it was all just for practice anyway. That was my thought process anyway.