why would they? The market for Windows, OSX, iOS etc dwarfs the linux-on-the-desktop market. It's business. Linux is for servers, OSX is for clients (and pesky Windows for the office because IT says so)
I don't see this changing anytime soon, and this discussion has been thrashed to death, I think that there will be dwindling support for Linux with desktop apps. The best you can hope for is a browser solution and that Chrome keeps building on Linux.