It's typical "you own nothing" logic to the point the companies selling you that also don't even own it.
- Disney -> Disney+/Hulu
- Universal/NBC -> Peacock
- Warner Bros. -> Max
- Lionsgate -> Lionsgate+
- Sony Pictures -> The Sony services relevant to the article (note: the Sony services sell more than just Sony Pictures content)
They never needed to, but it actually makes them more money because a revenue share model through Movies Anywhere makes sense. StudioCanal does not sell streaming/delivery services directly to consumers, a revenue share model between streaming providers would not make them more money, and Sony would have no influence on StudioCanal doing so anyways.
(I am a bit surprised they didn't bung Google and StudioCanal a bit of money to move them to Google Play to avoid the bad publicity though.)