But you can!
Mostly in Android though. I can confirm MIUI - the stock rom on Xiaomi phones - have this exact feature built in.
You can block all hidden numbers, all numbers not in your address book, specific numbers, etc.
Or one can use Tasker - an Android automation app to achieve the same functionality and more in any Android phone. I suppose these days, you can use Iphone's scripting functionality as well for the same, can't you?
Privacy concerns regarding MIUI /Android can be handled by installing a firewall like Netguard.
You can block all hidden numbers, all numbers not in your address book, specific numbers, etc.
Or one can use Tasker - an Android automation app to achieve the same functionality and more in any Android phone. I suppose these days, you can use Iphone's scripting functionality as well for the same, can't you?
Privacy concerns regarding MIUI /Android can be handled by installing a firewall like Netguard.