We’ve all written our fair share of code. Sometimes it’s elegant and well-reasoned, and sometimes it’s convoluted and flawed. No one is perfect. There will always be that moment where you look at code you wrote a year, a month, a day ago and say “What was I thinking?”
So it stands to reason when someone else is reviewing your code, or just happens to stumble upon it one day, they could have the same thought. Maybe they have a different solution in mind. Maybe they see a bug you missed. Maybe they just don’t like the way it reads. For one of a million reasons, they could decide your code is lacking in some way. And, in all likelihood, it is.