Because it's not just a platform, it's an audience. If you want to reach the audience, you have to use the platform. And the audience most in need of this message are definitely the people publishing on Medium.
I have a medium blog. I've had a few posts got >10k reads within a month. Almost none of those reads came from Medium itself, but rather from the various outlets that have linked to my post, and Google.
The only reason I currently use Medium is that people are more likely to open a Medium url when it shows up in link aggregators. People trust the familiar url far more than www.mypersonalblog.me - and it'll never get blacklisted / shadowbanned on reddit.
Oh, and claps. I like the claps.
I know this is just anecdotal, but I assume anything coming from Medium is usually less worthwhile. First, the author isn't important on a Medium article. Medium is the brand, the other is someone that doesn't matter. Secondly, it's not easy to follow the author, so even if I did read the author bio at the bottom, following the author is a pain. Finally, everything the above article mentioned. Medium articles are all about playing SEO games and "Growth hacking" before good content (literally). I'll ready Medium articles, but personal blogs are far more credible every day of the week in my book.
That being said, I would be interested in how you reached the conclusion that people are more trusting of medium articles?
Really just from my own experience. I've been writing and posting content for a few years and usually I get more clicks and comments when using the medium domain. (not always but noticeably more often)
That's a good point.