"Tired of being tracked online? We can help."
And then they track you.
Yes, that might not be intentional and is used "just" for the favicon, yes they might not use the info on the domains you visit for tracking you today, but the data is there.
Why not use that data tomorow "just" to see what kinds of pages their customers (browser users) are visiting so they can better place their ads.. and then maybe some other idea.. this is a path that many such companies went ("don't be evil").
You either respect the user privacy or you don't - there is no middle "just for this little feature" ground