Battles in that period were very quick just as they were in the Napoleonic Wars. Each soldier had a very limited number of shots, and in the american revolution, shots for colonial forces were scarce due to powder supply. Engagements were short an deadly. Companies would send a limited number of volleys down rage due to casualties or lack of shot. Artillery was not something to mess with. If you have read any Plumb Martin (first hand account of Northern campaigns) you can see the effect artillery had on men. At the siege of fort mifflin Martin described rows of up to four men being taken out by cannon fire by single shots. At Monmouth he described legs being snapped like nothing in front of him.