I find small food particles left on the top rack if I don't rinse. These are easy to remove (not baked on), but are super annoying and I can't understand why except that when rinsing it's reusing dirty water and not finishing with a clean rinse.
My dishwasher sends the water into the waste disposal built into the sink. If the waste disposal has a lot of food that hasn't been grinded it up, it seems to slow the draining of the dishwasher so not all the food gets drained before the rinse cycle. So I learned to run the waste disposal for a couple seconds before starting a dishwashing load.