Because any company, regardless of if they are a large corporation, isn’t going to devote time to code and maintain endpoints to provide data unless there are proven use cases for why users need that data. Additionally, UserVoice allows Twitch to see what sort of demand there is for a particular feature request so that they can prioritise discussion/implementation of it accordingly.
And the reason why companies listen, is because we’re their customers. 3rd party developers create tools, infrastructure, alerts, and so much more that increases the value of Twitch and the streamers on the platform. They have an interest in aiding us to build cool stuff that’ll enhance the platform. They may not agree with all feature requests, and even some that they may agree with could simply be too low priority or not technically viable to implement.
You don’t have to use UserVoice, but you’re only harming your own development options on this platform by not showing clear use cases to these features and how they can benefit not just your app but Twitch.