Germs on the peel can get onto the pulp "through" your fingers or a knife. Even if you washed your hands before cleaning, perhaps the 20 people who held the fruit before did not.
Once on TQ I came across the question: "Where do midges come from if you leave food lying on the table?" The answer to the question was: “The thing is that adults lay eggs on a ripe fruit, and when we buy an apple or pick it from a tree, we already bring the eggs of these flies home. However, for their further development, they need a favorable environment (processes decay), so the larvae patiently wait until the fruit starts to rot, and only then hatch and begin to actively reproduce. "
That is, if you wash bananas, oranges or other peeled foods well, you will be able to avoid the appearance of midges.
Unfortunately, yes, it is advisable to wash.
The fact is that the danger is not only that you can eat a banana with something extra on the surface. In this case, yes, we peel the skin gently and eat a clean banana. But it happens like this - you take a banana with a dirty peel and dirt gets on your hands from it, and then from your hands to everything around - on the handle of the cup, on forks, spoons, plates, on the table surface. And from the tabletop onto a piece of bread, for example.