I think the general answer is that it would take real development effort to make federation work, and having to have compatibilty with other installations slows down your own pace of possible features -- I think these things are undeniable. Arguably worth it for society/the community (I wish we had more open standard federation and less centralization), but from the point of view of the company will it actually lead to increased profits sufficient to justify? In fact, it may do the opposite, if you are one of the largest, then lock-in is better for your profitability. Compatibility with other services is only important for the small upstarts trying to get customers from the largest.
I don't like it, but I think we will get proprietary centralization as long as we have capitalism of the sort we have.