Depends on how much you let them link it back to you, but you’re absolutely right: social media is a privacy nightmare. It can be mitigated; pick a Lemmy instance that doesn’t require an email, and don’t give out any identifying information, or just lurk. Many of us have multiple accounts on different servers, with carefully segregated personas. You do what you can; OP asked why (or why not) scrob. I see no reason to give out that information, only to give a company more information they can sell.