In the few short hours since I started using #Threads, #DuckDuckGo has already blocked over 200 data tracking attempts. These include things like "headphone status" and "screen density."
Trackers, trackers and ol' Zucc's roboface galore.
Device fingerprinting. Even with unique identifiers turned off, if you have enough of these seemingly innocuous data points, you can track individual users across sites and apps, even without any other information. They can use this to profile you, and manipulate you.