I flew without ANY CHT or EGT gauges in many rental airplanes for decades....Lycomings (and Continentals) run pretty good without instrumentation. That said, the instrumentation is so cheap nowadays, and if it can save you a gallon/hour of fuel burn, it's not hard to see why most people put it in from the start. Especially when breaking in a brand new engine, seeing the CHT's, and doing something about an overtemp before you glaze the cylinder walls is pretty nice!
Paul