They apparently paid the author (Tito) to add it in. Originally he had pulled all of his packages from the default channel because he was unhappy that we require semver for all new packages (to allow newer features to work). After a bunch of users complained, he added SideBarEnhancements back (his most popular package), but apparently at some point later Kite paid him to add tracking code to it.
If an addon maintainer was successfully bribed to add something like this to their addon, that maintainer should probably be banned from the ecosystem along with everything Kite touches.
Kite is the primary corrupting force here, but the people who keep taking money to screw over their userbase need to be punished as well.
Sublime, Atom, and VSCode all need to step up right now and make it clear that this kind of behavior is 100% unacceptable
Edit:
Allowing this addon straight back into the Sublime ecosystem reflects extremely poorly on them as well.
Please see https://forum.sublimetext.com/t/rfc-default-package-control-... for the reason that SideBarEnhancements was re-added. In this case not re-adding it would lead to continued tracking of users, which seems to me would be the more negligent action on my part.
I'm not sure how Package Control handles removals of packages but if they are left installed in sublime then this was probably the best move.
If the package was left "orphaned" in the editor the telemetry would remain but I'm pretty sure PC updates packeges automatically by default so pushing an update without it makes sure the code is removed for most users.