When you use the site for the first time and search something where AI overview is available, it shows a toggle for how often you want to see it, with “sometimes” as middle ground being the default. Without showing that a feature exists, it’s hard to decide if you want to use it or not. And since peoples opinion about it seems pretty spit, I think that is pretty valid.

Or would you rather have a cookie-popup like choice box pop up every time you use the service without cookies enabled asking you for your preference? Because that would annoy me very much.