This has to be the most visible privacy control Google offers. Nobody is in Location History unless they turned it on, and if you have it turned on you get a reminder every month by email that says right at the top, in the snippet, "You're receiving this email because you turned on Location History, a Google Account-level setting that creates Timeline, a personal map of your visited places, routes, and trips. You can view, edit, and delete this data anytime in Timeline."