By "cast," you mean "tell the Chromecast to fetch/display content", rather than "show streaming video of my device's screen"?

This is part of what I'm asking: I don't get the usage model. I prefer using the STB directly with a remote (and no other client device), or pushing the client device's screen to the STB. If you're saying that you use "tabcasting" (which I guess is remotely-directed Chromecast web surfing), then fine. It's not something I'd ever use, but I understand that the equivalent doesn't exist on other STBs.

Please don't get me wrong: I would prefer if there were an open AirPlay equivalent that Android and iOS devices supported at the OS level. But I don't think that's what you're talking about.