They can't block it because it costs them nothing; there's no incentive to get them to build the capability. Currently it works like old school (physical, posta

They can't block it because it costs them nothing; there's no incentive to get them to build the capability. Currently it works like old school (physical, postal) mail -- the sender writes something on the envelope that says who they are. If every robocall received gets you five cents off your phone bill, it'll be solved within a year.