Early in my career I worked on legacy i-Series systems. One of things we were taught was to never write a code without putting in comments in the header. And the commends need to specify dates, ticket number for tracking, and the rationale behind the change. Every changed line had to be inside a block with the same ticket number, making it easier to simply Ctrl+F through the code.

Now I work on newer software and I frequently see people making changes without spelling out the rationale, dates, author etc. And it makes it harder to track what has happened and what does the code do exactly. When I tell people to comment it correctly they often reply about - how much time saving can be had by writing a clean code.