
India has the combination of being poor with a large English-speaking population. Both legitimate and illegitimate call centers are a thing there. In some cases the people are really doing it for the money, but there’s also human trafficking in India where people are forced to do the scams
It definitely used to be the case. Now I think more are elsewhere but it’s still a MAJOR problem. There also a lot in Pakistan. Russia has plenty, Thailand has some too. In some cases these scammers are held against their will in large office parks with armed guards and walls where they are forced to work if they want to eat. Those ones are lured with the promise of a high paying job.