The verge article mentions it's reasonably common and mentions some programs that do it.
From the article, a tweet
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They are far from alone, a quick `lsof -i | grep LISTEN` shows that I have: Spotify, Keybase, KBFS, iTunes, Numi, https://t.co/MVSAJgN9yY… All running locally listening web servers.
— Matthew Gregg (@braintube) July 9, 2019