[pwg]

> I've yet to read a good explanation of why the telcos permit ...

They (the telcos) are paid for every message they deliver. So absent regulation forcing them to do otherwise, it is in their best interest (additional profit) to pass through every message with no filtering of any form.

And, if the regulators had any technical knowledge at all, they would recognize that the billing system is the key to stopping the robo texts. Every text can be traced back to its origin through the billing system (because that's how the telco's collect their fees, so of course they know who to collect from for which messages they forwarded). So the regulators just need to force open the billing systems and trace the money back to the illicit senders, and then they know who to cut off (or to fine out of existence).