It helps users by providing apps.
Purism phone is very niche product. It is unreasonable to think that a lot of developers will start writing their application for PureOS. But hopefully some of them can port app if it will be easy enough. So instead of OS without almost any apps you will have OS with some apps.
Having been a user of Windows Phone, I would say, don't bother giving me an app if it's going to be garbage.