I think this is partly a second-order consequence of the reasonable expectation that, due to the rate of innovation and general churn in technology, computer-re

I think this is partly a second-order consequence of the reasonable expectation that, due to the rate of innovation and general churn in technology, computer-related information goes stale quickly and hence more recent sources should be prioritised. Having a date stamp on the page then becomes a liability (I for one am guilty of adding a current year number to my search terms for some queries to try to get more accurate results). Another reason might be that SEO got really good several years ago so older content just can't compete.