Because people have run analysis on the activity of the app already and the trackers don't fire if you aren't on the ad supported version.
All of the listed stuff is also required for serving ads through services like Google and pretty normal for ad-supported apps.
Have the various comment threads on a carousel once you click in. Because of the fractured nature of Lemmy servers I feel like I see way more reposts than on Reddit. It would be nice for them to get merged in some way.