Yeah you can blame Apple for that one. It's straight up non-viable to put up F/OSS apps into the app store. On a basic level, the GPL is incompatible with their codesigning processes and they have no intent of changing that (VLC ran into this wall
several times until they managed to work around it).
Putting that one aside (GPL is hardly the only license on the OSS field after all), the App Store model is just plainly too prohibitively expensive to publish a FOSS app for unless you're planning to maximize value. It costs 100 USD every year to just keep an app published (they charge this via their dev license). With F/OSS, budgets often are almost non-existent, so those operational expenses aren't made since they're not justifiable from a hobbyist, donation-funded perspective.
This is also why the platform has so many money-sucking timewasting "games" to be clear. Apple created a perverse incentive to basically ruin the App Store with stuff that extracts as much money as possible, then started selling people a separate subscription service to actually get games people do want to use.[0]
By contrast, the Google Play Store (Androids closest equivalent, albeit slightly different since Android has a far more open model[1]) is just a single 25 USD fee to prove you're a real human and after that there's no financial barriers.
[0]: Thats what Apple Arcade is.
[1]: The one difference between the Play Store and a third party apk installer is that the Play Store gets to ignore the installation request popup. This can be circumvented with root and apparently Google is changing this process to make it uniform when the Digital Markets Act goes into effect.