This depends on the latitude, but...You are watering at a time of year the rest of the plants probably dont need it. You create good conditions for fungus and other problems. You need to use pesticides and other chemicals that you would not use if not. You need to fertilize more, with all the associated environmental problems. You have bad transitions, sometimes requiring chemicals to kill of the Rye. You end up having bad grass coverage in the best times of year to play. You need to fertilize more after transition to allow the warm weather grass to have good coverage. If you seed correctly, you probably have to truck in additional sand. Additional gas used to cut grass all winter. Plus overseeding makes it more difficult to fight certain contaminations, like Poa Annua. At my latitude, all that trouble to avoid 2-3 months of dormant bermuda is not too smart or environmentally sound.