The business of producing a mobile app is difficult. After the hard development work, there's the process of promoting it, followed by long hours of supporting the app. Those successful at doing this can look forward to a long life for such an app, but without continued compensation.
I had the good fortune to sit down with Oliver Grahl, the developer behind the very successful PDF Annotator app for Windows. This app was released 10 years ago--an eternity in app years--and it's still doing well according to Oliver.
See also: App developers: Text size matters
The conversation with him quickly turned to the possibility of producing a version for Android or the iPad. This was fitting as PDF Annotator is specifically designed to work well on tablets.
I was surprised to hear him explain that, while he's given it a lot of thought, he has no plans to develop a version for those two mobile platforms. Having said that, I expected Oliver to express concern over the relatively low prices of apps in app stores, or perhaps over the cut that app stores take from sales. While those were concerns to him, they were not the main ones.
The biggest roadblock he sees in selling a version in an app store, is what he termed the "buy once" mentality of app store customers. He described that those buying a program in a mobile app store expect to buy it once, and then get updates without cost forever.
I believe in supporting developers of the apps I use, but I confess that I expect the same. It's not a conscious thing, rather it's become that way over an extended period using mobile apps. We buy the app and then updates are pushed to our device for free.
This makes it difficult, perhaps impossible, for developers like Oliver to make a sustained living off of a popular program. He's made a good living off PDF Annotator for a decade, because he's been able to charge extra for updates with major new features. His large installed user base has been willing to support his efforts by occasionally paying additional fees to make a good program even better.
But this mindset is opposite that of mobile app buyers, and is true for any mobile platform, even Windows. If there's an app store, we have come to want everything for little, and no ongoing, cost.
This has kept Oliver from producing versions of PDF Annotator for other platforms. He hasn't even produced a Metro version for the Microsoft Store. He didn't say that wouldn't happen, but he admitted his app is still doing well outside of the app store. Perhaps that will change in the future, but for now he has no plan to change his business model. Nor should he.