Even if your site is set up well to support it there is objectively less data you get back. Like it's hard to figure out where are the trigger points that increase or decrease conversion all that stuff. Or if people leave and come back. And it's a lot harder to run your own analytics (coming from somebody who does) even if you are just hosting somebody else's solution.

At that point what are you actually optimizing? If someone wanted to visit your site they would