They did try at times. The Paoli Massacre(Battle of Paoli) followed the disastrous Battle of the Clouds. Washington left Mad Anthony Wayne to harass the British while he went back to hold the line at Philadelphia. However, they were not fighting in the wilderness, the British held their families and their property hostage. The British forced a local blacksmith to lead them to Wayne’s men. The British had a larger force and were losing fewer men than we were in the Battles. So it’s not just the cavalry, it’s the threat of having them come after small fighting groups with a superior force and no place to hide.
I think also Washington may have reasoned out that he needed a surrender from British forces or the war could go on forever. It takes a long time to harass an opposing army to the point of giving up.