Wasn't the IRR always intended as the 'ready' manpower of a rapidly-expanded mobilization-based Army a la WWII?

If you're not mobilizing the nation, the recalling the IRR seems dumb. I know we have to do it because we're trying to fight 2 wars while not impacting Americans in their day-to-day lives (ie, rapidly-expanding in a mobilization-based Army), but it seems a bit stupid to me, and has for several years.