The source code to ed(1) is substantially harder to memorize, and the mobile experience is sub-par. ed(1) may seem to have strong user metrics, but they’re artificially inflated by users who don’t know how to close it and thus have kept the same session open since the early 1970s, making it difficult to inform them of other options.
https://www.gnu.org/fun/jokes/ed-msg.en.html