I think in professions that make use of lots of expensive, specialized equipment, the only way to stay up to date is through learning on the job or in a formal

I think in professions that make use of lots of expensive, specialized equipment, the only way to stay up to date is through learning on the job or in a formal training/educational environment. Programming is not like that. Pick any mainstream language, and all of the resources you need to develop a deep level of expertise in it are readily available, for free or relatively inexpensively. And accordingly, many developers proactively develop deep levels of skill and expertise on their own initiative. And my observation has been that these are the ones sitting atop the profession.