Retail bots and sneaker bots. Botters buy proxy IPs in bulk. When botters buy limited edition Nikes using bots, each “task” uses a different proxy, so they can increase their chances by appearing to Nike to be different customers. 500 tasks on a single shoe with 500 proxies and virtual credit cards looks like 500 different people when it’s really just one.
There are two different kinds of proxies (basically — there are more nuances I don’t want to get into): Datacenter (DC) and Residential (Resis). DC proxy servers are blazing fast but easy for a retailer to determine the traffic is coming from a datacenter like AWS so there is a high risk of getting the IP banned. Resis are slower but they are residential IPs so slower but less likely to get banned because they look like traffic from average consumers.
If the average buyer of proxies is buying 100+ IPs per month and IPs get banned constantly, proxy providers need a massive pool of millions of IPs running on residential addresses. That’s where these “free” VPN come into play. The consumer gets no-cost VPN, but their PC becomes an exit node for these residential IP proxy providers who charge people for the proxy access. There are tons of proxy providers but I think most are just reseller accounts of a few massive firms that run the show.
I am only speaking on the topic from a purely technical perspective. I do not want to discuss or spark debate around the ethics or people’s displeasure with the existence of botting and/or scalpers — you asked for a use case, and I’m only answering the question with a multi-billion dollar use case.