That's very different, that's a "botnet" style where you leverage consumer hardware and use them without their knowledge, similar to how you'd run a botnet farm for residential proxies (what Perplexity and so-on are using).

There is many ways of doing spam/fraud, think also that some are not very clever nor have good financial literacy, they just don't know the best mechanisms due to lack of education in tech (and the dark side).

For example, some would pay an infected residential network for $5 per GB, and some will only pay $0.10 per GB, depending on how knowledgeable they are.

Most calls/bulk SMS can be done cheaply by just buying Stolen VoIP enterprise accounts (available on a ton of forums), a "scam" operation will resort to any way possible because they don't have any law affecting them as they do so already illegally, it's not the same as "marketing calls".