As an example, depending on "man -w" not outputting anything to stderr: https://unix.stackexchange.com/questions/405783/why-does-man...
We removed the version and a few customers complained we broke their stuff.
Our back clapping was interrupted by an angry customer phone call. One of our customers had gotten access to our internal schema and had a massive reporting setup in Access solving most of his needs.
I ended up converting his reports using some internal tools we had. Customers will grab anything to give them.
[The caliber and depth of his reports were such I wish we would have bought them instead of making me spend months building out our own reports.]
Learning from customers is some of the best learning you can do. :)
This is probably an even more important principle in the age of LLMs.