It's the visibility, yes. I just moved my various blogging endeavors to one domain (coyotetracks.org) rather than the mishmash I've been using, which includes a few articles on Medium. But with only those few articles, I have over 400 followers on Medium, and my most popular article has 59K reads and 175 recommendations. (The next most popular has 39K and only 10 recommendations, because it's a criticism of "Mr. Money Mustache" and most people are hate-reading it from a link from his web site. Article #3 drops down to a mere 2.3K views, but 51 recommendations.)

I moved to hosting my own WordPress site; as much as I think WordPress's internals are a garbage file (actually, a series of garbage files passed around as globals, but never mind), it's so easy to make work--and the ecosystem is so big--that it almost makes up for its nastiness. But when I write an article that seems "Medium-esque," there's a very good chance I'm going to crosspost it to Medium to attempt to get those views. (With links back to my main web site, of course.)