Why? Typically you age an article to contextualize it (sometimes REALLY important). In this case it is an interactive educational tool, the age hasn't changed its purpose, value, or usage.

Because someone seeing the title might want to know if it's something new or the same thing they saw three years ago.

(Sometimes, new things pop up under a title that has been seen before)

I fully agree with you, but the fight has already been fought and lost.

HN regulars strongly prefer a year whenever it's not the current year, and the mods have confirmed that we should do so.

Added, thanks.