To be fair: since Mastodon doesn't have full-text search (just like Twitter did) and only hashtags are indexed for search: you need them in Mastodon to actually discover toots relating to a specific topic.
I didn't do the research, but I recon: that's why they where introduced in Twitter in the first place.
Ted Unangst is a core developer of OpenBSD, he started LibreSSL, made doas(1), signify(1) and lots of other stuff. Honk is an ActivityPub server (written by Ted).