When you blog on one of the other platforms like Medium, Facebook or LinkedIn, they own your distribution. The platform gets to decide how to use, who gets to see it and how to monetize it. In effect, who owns distribution owns the content. Posting to one of the big social media platforms can get more readership but it's a deal with the devil.
I made the decision to blog on my own domain because I want to own the distribution of my content. I'll certainly share it with the social media outlets, but the content will stay solely mine.
There's a tradeoff, of course. As just another domain blogging, I'm at a disadvantage. That's fine since I this blog is a representation of me and the most important thing is for me to control my message.