Theoretically, access to hype trains via the API, grants not just access to real time date, but to the historical data for hype trains (around 5 days iirc).
This means, in theory, you can use this data to help estimate the income of a streamer.
That, in my opinion, is why the API requires authorisation from the channel to access the broadcasters data.
Hype Train data belongs to the streamer and third party access to that data is governed by the permissions system.
TLDR: the data belongs to the streamer. The streamer will want to control whom can access it. And Twitch will surface only the relevant data to the front end to run the site.