theres too much stuff to memorize nowadays... its getting more complex every decade. e.g. If you have to load up in your brain XYZ security details about a certain cloud provider, and also understand caching, scaling, load balancing etc in a cloud environment, why would the person actively keep their 'OS paging' knowledge fresh the mind, its wasted real-estate. maybe certain developers with photo-graphic memory can do it, where they never forget _anything_ they learn. but most developers I work with have forgotten what they haven't used in 5-10 years