I don't think some folks/gov't realize what they are trying to accomplish is not provided by existing solutions.
Apple's 30% includes everything one needs to get paid for the apps that are sold on the store, and for Apple to handle all taxes and advertising on the store, their commission, etc. Taking out that 3% creates a new set of issues. Apple will no longer "see" the transaction. As it is happening outside of its pervu. They don't know if you actually bought it or not. They will then have to square up with that developer at the end of each month (or whatever timeframe they choose), and verify each transaction against the clicks to buy something from the app (IAP). This will have many if not way too many false clicks (nothing purchased but, button pushed). Clicks that did end in a purchase. Clicks that ended in a purchase but, the purchaser wants a refund. Etc, etc, etc,...
I don't think this is just a secure purchase issue. We all get that many institutions can do this securely. But, it's not as simple as say "Stick bank processing company logo here" and all done. "Which", of what is MANY processing companies are going to be able to be behind that button? That button is now code connected to that app on the AppStore. And we all know what EPIC already did with said code. That can lead to not JUST a redirect of payment options. It can lead to execution of other code that it should NOT be able to do. Other security related issue, changing the app by the developer and not seen by Apple. Any of which having nothing to do with payments.
So, Apple thinks lets just make a new app (clone the existing with these mods), that is built "FOR THIS". You get to use the 3rd party option (ONLY), so there is no link back to the app for security reasons. If the developer decides to change the processor or what that LINK does (malicously) . Well, it can only do 1 thing now. You click pay for this link in the app, it brings up the 3rd party option, and that is all it can do. Maybe if Apple had more time, they would build something more elegant. Maybe if they care about doing this, they would build something more elegant. But, that too isn't what they want to do in the first place. So quick and dirty it is.
The bottom 2 are my opinions.