Something that only came with the banking apps was opening of accounts via camera based identification and other security critical stuff, like 2fa for transfers, resetting card pins and setting other security features.
It's also easier to scan payments via app than go to the bank, something that is only possible via native like apps
No, the phone number needs to be known by the other party and you need to accept the "friend" request.
It prevents the creation of an unlimited number of signal accounts by a single user with no cost to the user but cost to signal and other signal users.
edit:
Your are probably right in that it does not change the risk of spam for a single user, as you could guess the phone number or just iterate over all known phone numbers and try to connect to them.
requiring phone numbers only solves the cost problem for signal(The company/legal entity) and lowers(hopefully) the amount of spam that would get send.
In the case of epic it was not about the privacy settings but about the percentage they had to pay for on every transaction which is a different issue.
I do think that it is a rare case that a company decides to not use the official appstore and the risk of all companies switching to their own appstore is minor.
Android does restrict more and more things you can do and there seems to be no strong movement to alternative appstores, which makes it difficult to know what impact the strong privacy settings on ios would be with an alternative appstore.
I kind of agree that less privacy protection this is a concern, but I think that should be solved by additional privacy laws.
At some point someone will need to issue a key, which at some point will need to be verified against known good signatures.
These signatures will also need to be kept in case of lawsuirs/enforcement, so if somebody gets access they will know you visited that site