Why aren't cell carriers liable for spam calls?

If I get a spam call, the originator of that call is theoretically liable - typically, some VoIP centre in India. Of course, they are impossible to track down.

Why not shift this liability to the last mile? If my carrier connects me with a spam call, they have to pay me the $500 fine per violation.

They could then have voluntary agreements with whoever they are peering with to pay the fine, sort of like how the financial system works. It would then cascade until it reaches a carrier who doesn't care, who would then be liable for the fines.

So:

1. I get a phone call. My carrier is AT&T.

2. AT&T got it from carrier C1.

3. C1 got it from carrier C2.

4. C2 got it from "VoIP Solutions Inc." of the Cayman Islands.

5. VoIP Solutions Inc. keeps poor records or whatever.

Then,

1. I ask AT&T to give me $100. They either do it immediately or lose their license.

2. AT&T asks carrier C1 to give them $100. If they don't, that's AT&T's problem, but they can depeer them.

3. C1 in turn asks C2 to pay them $100, and they too pay up (or lose their peering with C1).

4. C2 asks the Cayman corporation. They refuse.

5. C2 absorbs the loss and fire VoIP Solutions Inc as a peer.

The final link will always be a carrier with poor control over who is connecting to their network - in other words, enabling crime.

This is perfectly incentive-compatible, and it would have worked for e-mail spam too back in the day. It's quite trivial to implement. Why isn't it ever suggested?