To many things can come up with family or weather or parts breaking. Since Covid hit it's not like you can just over night parts and have your car up and running the next day like you could before unless you have a spare parts sitting at home. Most events that are pre-enter don't seem to want to give any refunds if you pre-enter. The big $ races that have limited number of entries are fairly easy to sell off your entry if something comes up before hand.