Yes, I had reservations in Kentucky at a small private campground in June. The place we were going to see probably won't be open by then. My cancellation policy at the time my reservation was paid in full was "at least 2 week notice you got a refund". So I cancel 4 weeks out and they inform me they changed their cancellation policy as of March 1st to state no refunds, just an indefinite "on-hold credit".
My guess, they've already spent the money, and have nothing to give back. Doesn't make it right, and I'm not sure in my case if it would even be legal, but who am I to spend $500 to get $120 back. In your case I can see how the multiple places would add up quickly, making a hurtful dent in the pocket.
If I were wealthy I would probably just say keep the money, it seems you need it, but I'm not wealthy. There credit may or may not be good in the future. They only reserve it by your name. If they go under or sell the campground, all those with credit are probably just out that money.
Sorry about the rant, your question just provided me a tee for me to go off a bit. I'm not a big fan of people using a situation to try and justify keeping other people's money.