You're missing the rest of it. It takes whatever you put in that dropdown menu and broadcasts it to the rest of the operating system including -- for instance -- your browser. The browser then uses that information to decide what to show you. The same would apply to any other app designed to receive it.

You can call what's happening in this thread a hissy fit, but how does that compare to $70 million in lobbying to get this added to operating systems? Isn't that a bit more of a fit? When you look at who is behind the bills, do you look at their history and wonder whose best interest they might have at heart?