Let me start by stating that i'm biased in favor of the matrix protocol...I don't see why google doesn't simply adopt matrix as its protocol and build a messaging client on top of that? Here are the benefits as i see them:
* The foundations of the basic matrix protocol are already built - so google can simply augment existing efforts and contribute to the project. And, they don't have to wrestle with carriers. (Any help for the matrix team seems to be good thing to me!)
* While, yes, most users wouldn't want to pay for such a chat service, google could tie this new chat service into their free gmail offering. I'm disgusted by my next statement, but i guess they could subsidize this for free users by displaying small text ads - just like in gmail - within the context of whatever matrix-compatible chat client they build.
* Plus, they can tie it into their Google Apps for business - or is it now called G suite? - and companies who DO pay for the greater G suite service will simply gain an additional enterprise messaging service which is similar conceptually to slack, and be available for enterprises as private server instances. Google could monetize this by adding a few cents to the monthly fees GSuite users already pay.
* By virtue of leveraging a decentralized/federated protocol like matrix - the users of google's matrix instances - either from the free or paid GSuite services - can STILL chat with users from other matrix server instances....not so differently in concept to gmail users emailing with non-gmail users. The cool thing about gchat back in the day was its support of xmpp, which i imagined help gchat's network effect...matrix could do the same here and now.
Maybe I'm missing something...but as smart as the people at google seem to be, I'm constantly dumbfounded by their chat/messaging strategies. Ah, well.