In the BeginningI started out developing for Windows Phone way back when Windows Phone 7 was the big thing. Your options for monetization were pretty much advertising or charging for your app. One great innovation that Microsoft provided to developers (and phone owners) was the concept of "Try" it before you buy it. This did actually help out quite a bit. With other platforms at that time (and some still today) if you, as the developer, wanted customers to be able to try your app before paying for it, you needed to create a special "free" version and publish alongside the "Pro or Paid" version that costs some money. That created lots of extra work and management. With the advent of Windows Phone 7 you could publish a single app with a bit of code inside that allowed a downloader of your app to play with it in either a feature or limited fashion and then when satisfied with the quality and usefulness just tap a button and update the app in-place to the full paid version. All the work they had previously done was preserved because it actually was the same app with the light switch turned on.
This was all well and fine but as with most "innovations" it tended to be a good starting point. Over the years of smart phones and app stores, many end users kind of got trained to look for "free" apps and, I think, had become averse to paying for apps. Not all users, but certainly many stayed well clear of paid apps not realizing there was a try before you buy model. I found this from personal experience.