But it's a default auto-installed app (on iOS9) and the headlines are on the search / Siri Suggestions screen. I'd be surprised if it doesn't already have a huge market...
So very few of those auto-installed apps ever see any use. iTunes (or "Apple Music", or whatever it's called now) might be the only exception.
I don't know whether there are any other stats out there, but I suspect that for most people, there's no need to install a custom podcast app, for example, when the default one works just fine for them.
[1] https://www.macstories.net/news/the-numbers-from-apples-wwdc...