Some programs offer ‘saver awards only’. Award space is available or it isn’t. You get a ‘decent’ price, or no option to book at all.
Other programs offer last seat availability, or access to most seats for points. But when fares are exorbitant, the algorithms can lead to some absurd results, like over a million miles for a one-way flight on peak travel days. That makes the program look bad, and even if members like “last seat availability” offering these seats costs too much to the program’s reputation.