Well, Ubuntu or any company could certainly do something like that. But then this company would simply be competing with Android with an incompatible app platform built on top of Linux. App developers who have a hard enough time developing their apps for both Android and iOS would not want to write their app for yet another incompatible proprietary platform, even if the underlying OS kernel was Linux.
As others have said, the real advantage to Linux, the real reason to use it, with desktop environments like Gnome or KDE, in spite of their minor flaws, is that the software is owned by all of us. Unlike proprietary software which you are basically renting for a monthly fee, on Linux you actually own your software and your data.
I use Xfce and Cinnamon, but I always install Gnome Terminal regardless (you don’t need all of Gnome desktop to use it). The main reason I like Gnome Terminal is that it is very simple, and it lets you save your own terminal themes and switch between them from a context menu. Xfce terminal is nice and simple, but doesn’t have this really handy theme switching feature.
That said, the terminal emulator I used most often is the Emacs built-in terminal emulator (
term-mode
), because it integrates flawlessly with other Emacs tools. But its rendering and theming isn’t as nice as Gnome terminal, so I only recommend it if you are an Emacs user.