California may try to help...Check this out: ktla.com/news/california/california-campsite-reservation-bill-passes-state-assembly/
Credit if you cancel before seven days. And if you don't show on the first night, the whole reservation is cancelled and the site opened up.
Maybe the NPS should consider something similar...
Check our our website: http://www.backpackthesierra.com/
Or just read a good mystery novel set in the Sierra; https://www.amazon.com/Danger-Falling-Rocks-Paul-Wagner/dp/0984884963