I hope there is a UWP version of Cakewalk Sonar in the works.
 
Be the first major DAW to support UWP!!! 

Oh, I forgot. FL Studio beat you to it with FL Studio Mobile 3.
 
But, I consider Sonar to be the big gun of the DAW world.

Is there some reason for that? As far as I can see win apps are very limited. They have use but as a DAW I'm not so sure.

The apps you've provided no examples of (I know what you mean) are limited because developers haven't taken to it. Image-Line on the other hand have shown what's possible with modern UWP apps in both Groove Studio (no longer available) and FL Studio Mobile 3 which runs on W10 desktop and mobile.
 
Sometimes developers act like old people longing for the past and familiar. UWP is here now:  A modern application model. Developers must meet the challenge.

mrdrwest@hotmail.com
Sometimes developers act like old people longing for the past and familiar. UWP is here now:  A modern application model. Developers must meet the challenge.

How do you know they aren't? 
 
You might want to ask Steam what they think of UWP...there are still issues that need to be worked out. The November Windows 10 update was a start, but if I was a developer, I wouldn't touch it for at least another year and give it a chance to settle down and gain acceptance. I just don't think the demand is there yet.

Ummm, it has to start somewhere. First it was sticks and beads. Then it was mechanical gears and actuators. Then tubes and transistors. Then integrated circuits and CPUs. Then flip switch programming, card reader, and assembly language. Then high level languages and frameworks.
 
Developers need to step up.

What I'm interested in are mainstream UWP apps that meet consumer needs, even if they're "reimagined".
 
This isn't about demand. The UWP is a new Windows 10 application model for devices. Windows 10 desktop has a large user base.
 
I want to see some creative modern/reimagined apps written for the UWP.

I can't see the point of a complex program like Sonar or any DAW for that matter being able to run on Windows Phone 10 as well as Win10

I own FL Studio for my Android - I could see the ease with which it (FLS) would be made available for a windows phone. IMO, "Sonar" on the other hand would need to be pared way back to just (eg) the Step Sequencer/Matrix to work effectively in that environment. More like Project 5 than Sonar. While I personally would love this, I would go iOS and Android way, way way ahead of UWP simply because of the relative numbers of the user base and therefore the size of the potential market.

This would 100% be near the very bottom of my priority list. Like was already mentioned, you'd have to reduce Sonar to something like a step sequencer to make it useful and honestly, that's not its strongest suit and definitely not what I use most. I couldn't conceive of multitracking drums or even doing serious vocal production on a phone or small tablet.