I'm guessing but the problem is source phone number spoofing. If Caller ID worked correctly 100% of the time and 100% of the time you get a fraud/spam/etc call

I'm guessing but the problem is source phone number spoofing. If Caller ID worked correctly 100% of the time and 100% of the time you get a fraud/spam/etc call you could complain and the authorities knew who owned the phone number it would be harder to operate the fraud. And with personal cryptographic attestation you could reliably link a phone number to a person.