In some cases, because they don't own a personal blog or website and don't fancy the hassle of setting one up. So whenever they have an article their existing s

In some cases, because they don't own a personal blog or website and don't fancy the hassle of setting one up. So whenever they have an article their existing sites can't host (because it's irrelevant to the topic), they stick it on Medium. For example, I could easily set up a personal site and post my random Medium articles there. But I already run a couple of more important ones with my time, and don't really want to spend time buying another domain, setting up my hosting, installing/customising WordPress and marketing the hell out of it when Medium can give me a decent looking place to put the content for free. There's also a built in audience at Medium. Not necessarily a large one mind you (the platform is much better at amplifying an existing audience than building a new one), but one that may have not come across my articles otherwise. Especially if I post my work in a publication. So that's my take on it anyway.