I think you just argued that we should go back to shareware. Free to download and then a one-time payment to unlock all functionality. That's also easy to support officially in the store and it's easy to add a filter for.
The problem with allowing IAP to be used for a shareware-like unlock is that there's nothing stopping shady developers from forcing a subscription on you later even though you already paid now. Forgot which one that was, but this kind of double dipping recently happened to a popular baby monitor.
Partner wanted to play all the time. I discovered the videos ads were using up all of my prepaid data before the end of each month. I bought the premium version, which was a one-time purchase "back then".
They launched an app revision that had a handful of very noticeable bugs. Then they changed to a new app (rather than upgrade), pushed all the users to the new app, and made the ad-free version a subscription. What do you get for your monthly payment? Well, nothing significant, like you'd expect from a subscription.
In fact, they essentially crowd-sourced their Q&A content by letting users submit feedback when a pair was inaccurate, so users are fixing problems in the content for free.
Server usage?
Not to minimize the daily work of countless devs, but a quiz game is essentially a handful of databases, a dollop of quite straightforward logic, some static UI visuals, and then content scraping to fill the main Q&A database. The logic and UI visuals almost never need a rewrite. DynamoDB is pennies per month per user, and if you're a real POS you can use long advertisements to push away users temporarily when your RCUs/WCUs are getting close to a scale-up threshold, which has the nice side effect of increasing revenue if everyone watches the long adverts anyway.
I guess they expected a percentage of users to bail switching to subscription, and that doesn't cost them a cent. You said it best: shady
To be fair, even if the payment is IAP, the publisher can still attempt double dipping, by first unpublishing the original app (which to be fair, while user-hostile, has the benefit that they don't have to bother supporting different/new hardware)
That's how drawing apps like Concept and Infinite Painter are priced. Free download, no sign up, several good features in the basic version.
There are IAPs to unlock brushes and other things, and a small fee to buy everything. I believe I paid $15 one-time to get everything for Infinite Painter.
The problem with allowing IAP to be used for a shareware-like unlock is that there's nothing stopping shady developers from forcing a subscription on you later even though you already paid now. Forgot which one that was, but this kind of double dipping recently happened to a popular baby monitor.