Ever heard the phrase "rabble of conscripts"? Napoleon was the first to use conscripts successfully; before him, it was proverbial that a smaller force of professionals (volunteers, landowners, adventurers, or typically a mix of all three) could wipe the floor with a much larger conscript army. Conscripts could make adequate garrisons, where they'd seldom be called on to fight (and if the castle or fortress fell, everyone in it would be killed, so there was that too), but not much more than that.