In most kitchens I've seen, the dishwasher is pretty close to the sink. In fact the sink and the dishwasher often share a shut-off valve. So if you run the water at the sink until it's hot, then start the dishwasher, it will get hot water.
Problem is, that most dishwashers have a prewash and a main wash. By the time the prewash is finished and the main wash starts, the water in the supply line will have cooled off quite a bit.
