hat is exactly why I no longer go to KOA's
KOAs aren't the only campgrounds who do this. Many private, Good Sam and others have the same types of policies.
Read the policies, don't like 'em, shop with your feet.
As far as why hotels can wait until the last minute, it's a totally different and more fluid market. And many hotels in resort areas have 14 to 90 day cancellation policies. OP had other options and opted to complain instead of trying something else. Ya pays your money ya takes your choice.