Just in case you unironically don't understand this and aren't just playing it up:
Allowing third party installations does not mean uncontrolled third party apps. It merely means users have to option to install software on their phones - which continues to limit the softwares capabilities until the user was prompted to allow each.
You could argue "but a braindead person can randomly go on a phishing website, randomly download some .app file and suddenly - through magic go through a theoretical installation dialog to finally explicitly grant this malware problematic permissions... And I'm sure there are going to be people that will do exactly that... But without it, they'll still manage to do the same to the same effect, just without the app installation by inputting their bank credentials in a phishing site or similar
The thing your citing as a problem solved by disallowing app installs isn't actually solved - and it would not become more problematic either.
Finally, the fact of the matter remains that almost nobody would actually use the capability to install from third party stores, as you've correctly insinuated. But if anything, that should be another proof that allowing third party installs doesn't reduce security.
People just like to have everything provided to them from a single source, and will usually pay a premium for that.
Allowing third party installations does not mean uncontrolled third party apps. It merely means users have to option to install software on their phones - which continues to limit the softwares capabilities until the user was prompted to allow each.
You could argue "but a braindead person can randomly go on a phishing website, randomly download some .app file and suddenly - through magic go through a theoretical installation dialog to finally explicitly grant this malware problematic permissions... And I'm sure there are going to be people that will do exactly that... But without it, they'll still manage to do the same to the same effect, just without the app installation by inputting their bank credentials in a phishing site or similar
The thing your citing as a problem solved by disallowing app installs isn't actually solved - and it would not become more problematic either.
Finally, the fact of the matter remains that almost nobody would actually use the capability to install from third party stores, as you've correctly insinuated. But if anything, that should be another proof that allowing third party installs doesn't reduce security.
People just like to have everything provided to them from a single source, and will usually pay a premium for that.