They're running the Software, but they're not on wordpress.com.
If we're talking about Software, then wow, Microsoft is really treating those game streamers well, because they can use it to play games which they stream.
Not really a good comparison. WordPress is comparable because it comes with the same/slightly different tools for building a business. It’s on the same shelf in the grocery store, so to speak.
I don't think so. YT/Twitch provide the platform and the audience, that's comparable to wordpress.com (in a way; it doesn't really provide the audience).
I don't know of any creators that are leveraging wordpress.com.
Using the software is like using Windows (or Linux, if you want a comparison in open source), but I don't think anyone argues that Linux takes good care of creators in the way they expect it from Twitch or Youtube, primarily because Linux doesn't pay creators, it's not a middle-man, it's a tool. Like wordpress.