I work in this field. The reason why robocalls are a horrible thing are two-fold:
1. Before SIP (phone calls over internet), only "reputable" companies had the capacity to originate phone calls, and everybody trusted everybody, so if Bahamas Telecom said the call was coming from Bob Dole's cellphone, then you knew it really was coming from Bob Dole. Now, with SIP, people can lie to, say, my provider, T-mobile because the SS7 protocol that phone companies use to talk to themselves was designed 40 years ago and is completely insecure. They've been talking about how to secure it for the better part of a decade. The phone companies (especially the likes of AT&T and Verizon) move incredibly slow. Google stir/shaken for more.
2. The phone companies get paid to let those robocalls come through to you. That's right. The spammers are effectively a (small) revenue stream for phone companies, so they're not feeling a huge sense of urgency about ending them. Their solution is to sell customers $3 and $4 add-ons for enhanced called ID and robocall filtering services, and profit from your misery, instead of having pride in what their network carries. If this were Japan, they would have shot themselves in the foot ;) . If Verizon lost money every time they routed a spam call, . It would light a righteous fire under their ass. As it is the FCC is prodding them to do more, but they're super late.