- Lots of companies are disorganized and have a poor grasp of what is going on inside them. I found it surprising how often in the workplace that clients would be ignored, agreements would be forgotten, meetings would be held with deliverables nobody did, "emergencies" would be deprioritized before the hotfix even arrived in prod, nobody would have a clue what I was doing for days, major features would get half-built and churned into the mud of Scrum management, etc. I've met contract employees who have been redoing the mobile app in every new framework every little while for job security. Native to Xamarin to React Native to Flutter. Nobody notices them doing that. In most organizations, I would bet that nobody is looking at the big picture in detail.
- Employment is now very short term and I am sure that changes how employees think. I just resigned from my current organization after a year. I was preceded by the product owner a week before, the communications lead a month before, the most experienced developer 5 months before, and the team lead 9 months before. On a 10-month-old project, half the people have departed. And I am not an anomaly. Plenty of friends from university are on their 2nd jobs as well (I am class of 2019). I have never known an employment environment where you aren't updating your resume every month. Why this matters is addressed by the next point.
- Resume driven development has long been a thing as you need it to keep getting new jobs. That is the term for the "hobbyist" work many developers do in their companies to stay relevant. People do it because not doing it helps you end up with a lot of old tech on your resume. A friend of mine is a Java developer. Not a software developer, but a Java developer. He only knows Java and only does Java. Where does he fit in a full-stack world? He doesn't. He has been unemployed for 7 months in a red hot software engineering market. Plenty of interviews later, most fall apart on the JS stuff which he is not inclined to learn. Obviously he could rectify this on his own time, but the point is that most backend only jobs have disappeared which is a major development shift.
I can't say whether it is common in the Bay area for a lot of "hobbyist" type work to happen, but it has occurred everywhere I have been to some extent. Not entire projects usually, but who does what work, the tech stack used, and whether a library is used instead of a custom component.