> What confuses me about this is that Apple could solve this in two seconds by allowing contact whitelists where only incoming calls in your contacts are accepted and everything else is sent to voicemail or dropped.

Now you missed the reminder from your dentist, a call from that relative whose new number you forgot to save, and you have 600 recruiters and other stale business contacts in your address book because you wanted to hear from them but you're still getting spam calls because the spammers were smart enough to start spoofing numbers like the local utility companies for your area code.

There are many technical fixes which sound good until you think about what an adversary with a profit margin would do to work around them. What will work is fixing the underlying telephone system so Caller ID / ANI are reliable enough to use for filtering and law enforcement. The major telephone companies didn't want to spend the money last time, and they profit from all of these calls now, but if it became a regulatory requirement that would change.