Right now a large part of the Southeast is experiencing very dry conditions. Since the soils in the Southeast are made up of primarily clay or sandy soils Topdressing with compost can be a big plus. The compost in the clay soils helps granulate the soil increasing soil particle size so that water can permeate the soil better and the compost in the sandy soils helps retain moisture that would have other wise just passed on through. I just recently returned from a trip to Georgia where I saw lawns burning up due to lack of rain. Lawns with very little organic matter have a hard time holding moisture.
The end result is lawns that burn out faster.