Mine: require setting a URL to support password managers. You download an app, go to login, tap the password field, and open Bitwarden. Does it find your login? Half the time, nope! The dev didn’t tell Apple one time what their URL is, so everyone now has to search their password manager every time.
Problem is that requires carefully testing, and not every company wants to have a half-assed port that doesn’t have a good experience on the desktop.