People are bad a predicting future. Especially when this predicting is done in 5 minutes before implementing something and not dedicated activity which includes interviewing of users and domain experts.

I've seen this many times: programmer is asked to solve a small and well defined problem. Instead programmer generalizes it and makes something more universal with the requested feature as a special case. More often than not nothing except this special case is used.

Or working on some new project they add a feature which looks useful in theory, but ends up being rarely/never used. It may look easy to implement initially, but over the years maintenance cost can be much higher.