[babyloneleven]

You are the site owner. The bouncer works for you.

Your users didn't hire the bouncer and don't want to be tracked. Secretly, the bouncer may use this data for nefarious purposes. You can't control how the bouncer will use the data.

[mojuba]

Exactly, especially if the bouncer comes to work for you for free. Which is what Google and Facebook analytics platforms do: they are free because they benefit from the collected information in ways beyond your control.