Fwiw Twitch is now owned by Amazon, not sure if it was/is profitable though - but it may be that the cost of such massive video platforms is too high to run without a parent company that can subsidise the costs.
In the case of Google/Amazon this makes additional sense because they own the cloud infrastructure, which I assume is the biggest cost of the platforms.
Twitch's feature set is not that different from YT's at this point. They both have very elaborate streaming services, a financial support mechanism, viewable archives with seeking, automated muting for copyrighted content, and recommendations systems.