IMO the Power App license should only be required for "power app builders", but not for each and every app consumer (which will go into the hundreds/thousands in many cases).
I am building power apps mostly for SharePoint Online. These apps have touch points to other things using Microsoft Flow, like Yammer and eMail. In this scenario, I would like to be able to simplify the experience for app consumers, so that it is more like the experience they had when an InfoPath form was created for the list they have access to. They automatically can use Power Apps to interact with the data without having to sign up somewhere else, and without having to add an unexpected cost to the business (in the case that Power Apps ever get a pricing model and are no longer free).
Benefits of Focusing on the Designers/Developers of Apps rather than on consumers:
-License management is a bit easier to handle (most form designers are more technical and don't mind having to sign-in multiple places to get stuff done). End Users on the other hand aren't so happy when you ask them to bounce around with their credentials. (sign-in to office 365, sign-in on the app when opening power apps, often another sign-in to integrations in the app; is more than enough signing in for the typical user).
-Enterprise can force data collection through the app if it fits the business requirements/scenario. (Not leaving it as an option for sales engineers etc.)
-Enterprise can manage the designer community better. Being aware of who is designing, versus consuming Power Apps.
-Enterprise can block / clean-up mismanaged/unused accounts (that ultimately might result in additional costs at a later date)
-Enterprise can predict costs based on an evaluation of how many apps are published.
FYI: IMO it would be cool to have the ability to create an 'app builder' domain group each departments, and the domain group could be given the license (perhaps through Power Shell as the result of an AD property specific to that role). This way app builders would have an instant network to rely on within the member group/Delve, organizations would have a pool of app designers easy to connect with, and they could be dropped out of the group to remove individual licenses when necessary.)
Licensing does distinguish App Makers from App Consumers. For example, notice the p1 and p2 plans outlined here. The P2 plan being required for app makers modeling data from CDS, but is not required to consume those same apps that have been published for consumption.