Even though they can't read your messages, they know who you talk to, how often, when, and for how long. They also track your device info, IP address (which can reveal your location), network details, and app usage patterns.
And this data isn’t just sitting there—Meta uses it. For example, if you chat with a business on WhatsApp, you might start seeing ads for that business on Instagram or Facebook. They don’t need to read your messages when they can infer so much just from how you use the app.
Disclaimer: Comment translated from Spanish and corrected by Chat GPT.