The largest market of Mobile phone users are not tech people.
They're average Joe and Jane just trying to get by in life, they probably don't even use a computer in their job. They use their mobile as a means of contacting loved ones, taxi etc and will use it for light entertainment be it a youtube video, app gaming, or quick lookup of information.
I'd argue that most mobile users don't even use email on their phone for anything more than that annoying after thought of registration and confirming they've registered for sites or apps.
Most certainly don't have anything more than an old outdate or a very under powered laptop/PC that already leaves a sour taste in their mouth thanks to all the malware they've got installed, constant crashing and just overall slow working machine (as seen by them as slow windows), then they have the whole bothersome problem of lugging it around and trying to type and use a touchpad/mouse.
Yes for us tech users it's super easy to think of a PC as a pleasure to use and the touch screen keyboards on mobile devices as terrible for doing any worth while work, but guess what? The majority of mobile users out there, they're still not using their mobile to do any work, or even anything even remotely productive.
For those that are trying to be productive, they're using the same methods as everyone else before mobiles and the smart aspect just delays their need for a real PC at the office or pulling out their laptop. You can argue that the continuum experience would help mitigate that, and that they could just do everything there and then, but that's not the world of productivity we work in. You are going to have to work with other people, you are going to have to work in a flow with other people and that doesn't (unfortunately) consist of you pulling out your laptop or mobile phone with continuum to work on things while they're busy trying to move on with their flow of work.
There would have to be a huge change in the way everyone works for that to happen, and it's not happened with laptops, even the ultra mobile ones. It's not going to happen with a mobile phone platform that the majority of people don't even care about, let alone use.
And that leads me on to the usage of it. To get people engaged into a mobile platform, and what is effectively just an 'app' for continuum as seed by anyone who's not into a tech, it's an app that runs a some basic forms of Windows like software, and that's all it does. They don't have Windows 10 machines on the whole, a lot don't even have a PC in any form anymore so they can't even relate to it... and these same people are the ones that flash off new features and tacky apps/games to their friends and work mates for a bit of fun and giggles.
Microsoft is now a decade behind the mobile movement, and there are teenagers growing up now without a care in the world for what Microsoft means. They're going though school with chromebooks, or even buying into the high flying life style of mac books or even ipad pros. None of their friends, or even teachers will be using Microsoft mobile. They get a cheap Windows based laptop to produce some word-processing, but you can almost guarantee apart from visiting some porn sites, out side of study hours it'll be left for dust.
So what options does Microsoft have for the people that produce the movement in tech, our younger generations who're buying into the new tech devices that Microsoft is seemingly not part of anymore?
Xbox.
That's what Microsoft can connect younger people with, and they do. Parents are more likely to buy a game console for a kid as a gift for say Christmas. At this point Microsoft could double up with continuum on the xbox as an app leveraging the power of the app store on Windows 10, for the next generation of children/teens growing up, keeping them into the eco system, and maybe when they see what continuum has to offer they can move on to something Microsoft Windows based, if nothing else it's going to keep Microsoft at the for front of their experience and for parents, they get a productive machine for school work as well.
Other than that, I don't see Microsoft progressing anywhere other than business usage and hard-core gamers /and/with VR moving forward.