2. Killing Bacteria and Microorganisms.-Hot water is needed to effectively kill bacteria on dishes. It may seem like you can squeeze a little more use out of a dishpan full of cool water, but compromising your families exposure to bacteria is not worth the extra trouble of running a new pan of hot water.
3. Cutting grease.- Water temperatures under about 90 degrees will leave a nasty greasy film on your dishes as they dry. Grease cutting ability is severely hampered by cool water leaving your dishes less than clean.
4. Drying Time- Hot water dries much more quickly on dishes than warm or cool water. Dishes can essentially dry themselves if the water temperature is right. As an added benefit, dishes will dry spot and streak free with hotter water. Many people try to conserve hot water during the rinsing part of dishwashing and just hand dry dishes. Keep in mind that pools of water and wet dishtowels are a haven for bacteria. You may have just spent a lot of effort to get dishes clean only to allow them to become contaminated.