Interesting! Do you have any clue on why these websites are being made? Reddit also has many aggregators, but some of them are literal blogger websites.
HN is a relatively simple, well understood web site, and there is an easy-to-use API that one can get access to without much ceremony. It's almost as common a "getting started" type project for a new front-end framework as creating yet another todo list app.
I've assigned it as a take-home project for job candidates before.
