If you make the carrier liable for damages in case of fraud, there would be process to mitigate the risk from one bad actor. Like the bank requires a manager approval for certain high risk transactions like international wires.
Too long of a moon shot. Generally the T&C are limited to actual loss, like you lost your internet for 2 days so they'll reimburse you for 2 days of bill but not if you lost a business deal. Similarly in case of airline if you missed your game. they're not responsible for the game tickets
That would be smart criminal with means. I was thinking more of a hood with fat neck passing $20 to clerk assistant to obtain SIM for $5k fraud.