Competence with dumb bombs requires training. Continual training, regardless of whether a conflict is expected or not. It's not a skill that can be kept on the back burner (at least, not if you want to get the things within a vaguely effective distance of a target while under fire). Better to spend the cash equivalent of all the flying hours and airframe fatigue on a bigger stockpile of guided munitions, IMHO. With flying hours a scarce resource, it would be perverse to spend them training for a back-up capability if that came at the expense of primary capabilities.
An alternative question arising from the conflict is whether the likes of HIMARS and ATACMS can supplant combat aircraft in the CAS and BAI roles. Why impose all the fire support coordination measures necessary to avoid blue-on-blue, and expose aircraft to severe risk from short, medium and long range air defences over the front line, when a land force can just employ precision guided weapons of its own from deep in the rear and keep its air defences at weapons free (which is likely to be essential for dealing with pop-up drone and cruise missile attacks)? Sure, guided missiles are expensive, but so is a combat air force with all the training, datalinks, and self-protection systems it needs to be effective in such a difficult operating environment.