isn't there some application for hardware attestation for calling? Like if I get an iMessage text I know its a real person with an iphone, but no similar system has been applied for phone calls. It can't be that hard for carriers to provide some kind of indication whether a number is an actual phone or not.

There are massive armies of cheap Chinese phone bot farms... I don't think getting spam from a physical phone is any indication there is a real person in the mix.