"In this post, I will discuss features of freemium products, which I work with mainly, and introduce the complex parameter F-Growth, which is useful both for internal and external assessments of freemium products, especially from the viewpoint of investing in and marketing them. " - Ilya Osipov
https://www.academia.edu/9898537/Virality_Retention_and_their_Interrelatedness_via_F-Growth
https://www.f-growth.com/
So, as a caveat, this aside is not about private, internal apps for internal business issues. It is for creators of commercial products.
Apps need user growth in order to succeed. The app needs to be designed in such a way that it grows itself on its own. I interact with developers who are toying with technology and developing complete programs that function as expected, however, as a product, they will go nowhere because their current users don't attract enough additional users.
The trick is to develop an app that serves its functionality but also encourages users to refer the app to their social network or even demands the network effect to engage.
Usually, when the app is successfully developed, the problem becomes one of discovery in the app store. With a couple of million available apps, the user probably won't find the creator's app. Then the issue becomes how to market the app to the internet to drive sales.
The options for marketing efforts run the gamut from Kickstarter/Gofundme campaigns to paid ads on TV or radio.
All of these take the time, effort, and money of the app's creator to execute.
The better option is an app that is designed to promote the network effect or, at a very minimum, encourage its users to invite their friends to also download and pay for the app. In this regard, the app's users voluntarily take up the marketing efforts and costs associated with gaining new users at much less cost to the creator. This is the key to a successful, money-making app versus a hobby is the f-growth.
Using the formulas related to calculating f-growth, an app creator can quickly and easily determine if the app is worth pursuing in the first place before any wireframes or coding starts.