I cannot think of a legitimate purpose for residential proxies existing. They take advantage of people who don't understand what they're being asked to give "consent" to, and then offer up those people's internet connections to whatever actor wants to abuse it, including malware authors, aggressive scrapers, and anyone with ill intent.
Why do you think this rampant abuse is a good thing? What benefit does this provide to society?
Also these proxies are against the terms of service of every ISP.