This is one of many reasons I don't make reservations most of the time. We've driven in early during the day and never been refused. We if couldn't stay, just move on.
Other reasons: Bad facility, bad location (ie. tracks, trucks, planes), less than intelligent clientel, bad weather, small spaces or too tight, high prices.
2015 Fleetwood Discovery 40E on a Freightliner XCS chassis with a Cummins ISL9 pulling 1 and/or 2 motorcycles, '07 Honda Accord OR a 17' Runabout Boat.