They dont actually thanks to VoIP and other countries telcos being shit and pushing through whatever is sent with the call, which is exactly where that disconnect happens. Ive been in Telecom a long time, and the push to fix that problem was very real long before Indian scammers were spoofing calls for IT scams. Once you go to IP, the “real” link isnt there, and CID becomes no more than a data string which is no longer tied to anything physical as far as telecom infrastructure, which they have to accept in the current set up, which is why said the whole thing has to start from scratch.

The other issue is the way non ILECs send the CID is exactly how the scammers spoof, to cut that off, all CLECs would loose the ability to send CID data, businesses wouldn’t be able to send a main phone from their 3000+ extensions etc. Its far from a simple soulution which is why its still an issue.

You can be damn sure that functionality was a top priority from day 1 because (just like for all subscribers) they need to know the spammers’ usage in order to bill them for it.

CID data being injected has absolutely nothing to do with a line being used regardless of what the outbound DID actually is.