I believe at least one of the business models for "free" VPNs is to turn their users machines into exit nodes, and the real business is in selling those to peop

I believe at least one of the business models for "free" VPNs is to turn their users machines into exit nodes, and the real business is in selling those to people who want to spread their traffic across many residential IPs for usually dubious reasons (e.g. scalpers trying to scoop up concert tickets or limited edition sneakers or whatever without tripping bot detection).