"AI agents" can't do much without access. To wring value from them, people grant them access — to social media accounts, to credit card info, to school, work, insurance, etc. That gives the AI vendor access to troves of data they couldn't have gotten at otherwise, which can then be used to build stronger, more comprehensive, more intrusive profiles, not just about the AI user, but also anyone else who appears in their data.
They're potentially the most effective surveillance machines ever made.