Because that is what is happening. People who get kidnapped and refuse to work are being murdered. This isn't call center work. Some people may be doing this voluntarily around the world, but this article is specifically about people who are being held as literal slaves with zero chance of walking out alive on their own free will. And it's worsened by the fact the governments of Laos, Cambodia, Myanmar (or what's left of their government), and Thailand are all complicit in this. It brings in big bucks, and there are reports of police even bringing people back to the compounds if they somehow escape.

The captive ones do the scamming via text anyway, and they'd get beaten or worse if they don't do as wanted. "Just send some coded message", your incompassionate mind might say.. sadly not everyone is as wise as you, and it's hard to be so when they can cut your head and throw you into a river in a lawless part of the world.