At this point Google pretty much controls the future of web-oriented internet protocols, since they control the client in the form of Chrome, as well as the server in the form of Google properties. What they do is basically what goes.

People inside of Google were putting together HPKP at the same time that we were putting together TACK, so that was pretty much the end of TACK. HPKP is really simple for Google (just pin their own CA), but isn't as clean for most other major sites (who are stuck with many CAs). It also doesn't offer a layer of indirection away from CAs, which again, is not an issue for Google (they already have a layer of indirection in the form of their own CA), but is less ideal for the rest of us.

It's better than only being able to hardcode pins in the browser binary, but it's a shame that it doesn't take on some of the other pain that's come up with pinning.