Many state parks in WI are VERY popular and nealy all electric sites are reserved 11 months in advance. A few years ago WI DNR changed the rules to be similar to that of FL, if you don't occupy by the checkout of the next day, you lose the site. The reason for this is that people were reserving 21 days worth of a site only to use it on the last weekend. Yes, they would actually pay that much money for a few days use.
Being that it is so very hard to get into some of these parks, when people do this its simply not fair to others, especially to those whose taxes also pay for services in those parks.
BTW, I don't have a fundamental problem with someone leaving a unit on the site for a few days and fully occupying later. At least it shows "good faith". But reserving a site at a publicly owned property and not occupying for days or even a week just comes off as selfish.