Yeah but what are the chances that someone from the hiring team will call an old reference and get told the story about how said developer's shiny thing chasing

Yeah but what are the chances that someone from the hiring team will call an old reference and get told the story about how said developer's shiny thing chasing caused them a lot of pain? What are the chances that the developer gets a big raise from the new job because he has experience with a desirable shiny new technology? The reason we have this phenomenon is that companies highly value (or even overvalue) experience with hot new technologies. So even if as a developer you know that maybe kubernetes, microservices, and NoSQL [or whatever it is] are not right for your organization, you know that having those on your resume will help you get a big raise and a promotion on the next job. The chances that your new tech chasing misadventures will haunt you in future jobs is very low.