https://appleinsider.com/articles/24/02/23/apple-makes-its-own-app-store-less-convenient-in-eu
TLDR;
The Apple App Store is too easy and intuitive for Apple users, and since 3'rd party stores need to go through more hoops the EU is forcing Apple to implement those same hoops in their UI and processes to level the playing field.
Note: Apple later commented they are keeping the functionality on the back burner incase they need it, but it wasn't supposed to be deployed yet because the EU hasn't ruled on that yet, they will be removing the extra prompts in 17.4 but may need to bring them back later if legally required to.
TLDR;
The Apple App Store is too easy and intuitive for Apple users, and since 3'rd party stores need to go through more hoops the EU is forcing Apple to implement those same hoops in their UI and processes to level the playing field.
Note: Apple later commented they are keeping the functionality on the back burner incase they need it, but it wasn't supposed to be deployed yet because the EU hasn't ruled on that yet, they will be removing the extra prompts in 17.4 but may need to bring them back later if legally required to.