The implication is that the users that are being constantly presented with CAPTCHAs are experiencing that because they are unwittingly proxying scrapers through their devices via malicious apps they've installed.

When a random device on your network gets infected with crap like this, your network becomes a bot egress point, and anti bot networks respond appropriately. Cloudflare, Akamai, even Google will start showing CAPTCHAs for every website they protect when your network starts hitting random servers with scrapers or DDoS attacks.

This is even worse with CG-NAT if you don't have IPv6 to solve the CG-NAT problem.

I don't think the data they collect is used to train anything these days. Cloudflare is using AI generated images for CAPTCHAs and Google's actual CAPTCHAs are easier for bots than humans at this point (it's the passive monitoring that makes it still work a little bit).

Trojans in your mobile apps ruin your IP's reputation which comes back to you in the form of frequent, annoying CAPTCHAs.