It are not illegal services, they are just stretching the law to its fullest.
Its whit like some of the SMS services, most of them follow more ore less esthetically rules but some of them abuse the system to its fullest and try to get top dollar for minimum service

So Google can only block them, suing them would be pointless

Yes, calling the cops might get the fraudsters in jail, but that does not mean that Google gets the money back from the scammers.
It is so common practice that companies take measures to reduce their losses to crime that it would reflect bad on Google if they did not stop the leak. Going through the trouble to recoup the money generally isn't worth it as it most likely will be spent. So best is to give the fraudsters no money at all in the first place.

Would make more sense they'd call the cops or sued when they are being scammed, it's not like they can't afford a lawyer.
Thinking of blocking as a first response is something someone that is evi.. wait they say they aren't 'evil' so that can't be it.

We cancelled our mobile cell phone service because O2 was blocking calls to a local access number for my prepaid calling card. I strongly urge neutrality as a matter of policy.