A useful example includes the ordinary complication that a perfect example politely removes.

Clean examples are built by removing everything that would get in the way, which also removes everything the learner will actually meet. The tidied version teaches the principle and leaves the person unready for the first real case, where the data is messy, the customer unhelpful and one field missing. Difficulty is not noise, it is the subject. Teaching that skips it produces a confidence that fails on contact.

When you are showing somebody how something works, use a real case with its awkwardness left in. It takes longer, and it is the part still useful when you are not there.