Students still forgot in the first year but got heavily marked down for it. It quickly got etched into your brain to date and version just about anything you did.
Today when I see an undated blog entry it seriously affects my perception of the writers integrity.
Yes, but you see it. The canonical reasoning I've heard for missing dates is that it avoids SEO penalties for old content.
I await the realisation of the Hitchhiker's guide's remedy for the Marketing department...