Ubuntu Touch was expected to have that. It makes a lot of sense. Your phone is already running a Linux kernel. You should be able to create a chroot or a container system that has a standard Linux distribution. You add some hardware hooks, some data sync apps and you should have a Linux desktop hidden in your phone.
Yes, and it took around 20 years to go from the patent for the first underpinnings of applications for phones other than communication in the 1970s to Simon Personal Communicator in the early 90s, and then another 10 15 years for the first smart phones to emerge. If people gave up because it "had been tried before", we wouldn have any of the technology we had (in fact, we would still be planting crops with wooden sticks because Thog got trampled trying to chase some wildebeest off of his early attempts at farming). You can use any windows 10 device as a screen but usually the laptops I have near me are mine, so they already have everything I need. You put your powerpoint slides on the phone, and if all else fails you can project your slides to any w10 laptop that near.
I love it!I owned an Atrix with a lapdock, which was the first device to embrace this concept. It was a good device, just hampered by the lack of RAM, the dual core processor (which was a bit sluggish), and the hampered Linux desktop; I too hacked around with it to be able to install all manner of useful tools (compilers, editors, office packages) and it was useful. The Lapdock had a good screen and was conveniently incredibly thin.
They don want that. No one is sitting at a desk unless they working or gaming. The tablet keyboard is enough and way more convenient for most users. There is a ton of talent and time being wasted on a feature no one really wants. MS, the only big company trying for this feature (and failing hard), can waste all the time they want, but the worlds needs a competitive open, general purpose mobile device and the projects keep dying because they can figure out a good way to implement a feature no one needs (because there is no good way to implement a feature no one needs).