Users are now getting Android's convoluted sideloading process, and everyone hates it
(www.androidauthority.com)
Normies keep falling for scams all the time. They fall for scam on windows, over the phone and in person. We generally try to come up with rules that protect normies without overly complicating lives for everyone else. Like I have to go to a bank personally to increase single transaction limit over certain amount but I don't have unlock some secret options and wait 24 hours every time I want to wire money to a new account.
A warning saying "this app is not trusted, don't install it if someone else instructed you to do so" would be enough here. Advanced users should be able to disable this warning. That's it.