That's probably where some of the proxies come from.

The end user typically has their device compromised by using free apps where the developers were bribed $$$ to add the proxy "SDK". The botnet operator then rents out the bandwidth at exorbitant rates to anyone who will pay for it.

Chrome extensions are also a huge source of this, they look for extensions with a large install base and then make an offer to buy it to turn all the users into proxies.

end users install shady VPN apps/extensions to watch pirated content, and become part of residential proxy mesh/botnet

If by “some” traffic you mean botnets, sneaker and ticket scalpers, scammers, content scrapers, credential stuffers … generally scummy stuff, sure.

Based on this blog post I would not do any business with Skyvern, if they indeed do business with this underworld of bottom feeders.

Sure, if you want a whole bunch of legitimately malicious traffic to be attributed to your internet account.

Yes. Google “honeygain”