Throughout the first two series of Sherlock, Mycroft sends a car to pick John up and bring him to him. Just about every time, they meet at a different location. He doesn't seem to have any issues with protecting his identity (once his identity is revealed). His only concern, and it is only an occasional one, is to prevent Sherlock from being aware of the meeting or what is being discussed.
Why does Mycroft meet John in different locations?