Developers aren’t doing ad supported apps because of the 30% “tax”. Did software sell with ads when they had to pay physical retail stores 60% for distribution?
They do ads because people are too cheap to buy apps.
Getting 30% less ad revenue means that subscription revenue would look marginally more attractive. Some # of apps would switch to "paid" if the tax applied to ad revenue. And maybe some apps just wouldn't get made at all, if they were already on the margin of profitability.
Most of the most profitable apps on the store are free to play games with loot boxes and in app purchases or subscriptions - and most of those aren’t even accepting purchases on the App Store anymore.
If Apple reduces their “tax” to 15% how would that compensate for not having the ongoing revenue of ad sales?
There are doubtless cases where that extra slice of one-off revenue per customer would make all the difference in the world to the business model.
At the same time, I suspect that in most cases it would not change the business decisions being made. Recurring revenue matches the financial needs of a business better in most cases.
I am not able to point concretely to any. As I am not possessed of sufficient internal fincancial information to evaluate the question, I am also not equipped to evaluate the question.
I do feel safe in suggesting that across all the apps of the world, there is a greater than 50% chance of there being at least one such application.
If they wanted, they could ban ads, end of story. This would be the equivalent of the retail distribution. They could open up their platform so people could install software outside of the app store.
They do ads because people are too cheap to buy apps.