From the beginning of my career in web development I worked in companies that had good to great monitoring capabilities in place to log and measure performance, resource usage, availability, errors, etc. in all parts of the system. so I took it as something self-evident that you would add that first thing, before deploying a new project.
Only recently as I started mentoring people in other companies did I realize that many developers or not aware of what exists in this space.
In two cases I got asked for help to deal with performance issues, and in neither case did they have any idea what was causing them, because they had pretty much no tooling to tracking it down, so they resorted to speculation. We installed a application monitoring solutions and they were able to fix the problem in no time once it was identifiable.