You won’t be signing up for many races, then. There are a few that will give you free or discounted entry in the following year’s race if you can’t run but not many. It’s not pure crap, though. Many of the expenses associated with a race are flat fees that they charge the runners based on expected number of entries (ex: closing the streets and police protection will cost $5000, we expect 500 entrants, that’s $10/entrant). Other costs to the race, such as t-shirts, were probably already paid by the time you knew you couldn’t run. If races gave refunds or credits for the following year’s event, entry fees would instantly rise.