In focus tracking, the newer cameras use info from the color matrix meter to determine if the subject has moved off your chosen focus point and can switch to a different AF point to continue accurate tracking. For fast moving action with high magnification i.e. birds in flight, this can be a tremendous advantage.
On the 51-point cameras I use this in a limited fashion (9-point or 21-point) since I have had situations where I panned with a bird launching off a perch, and in review, the AF point followed the perch off the edge of the frame as I panned. Remarkable tech, but of course not what I wanted. Limiting the number of active focus points lets the camera know, yes the think near the middle of the frame is where I want you focusing.
In landscape shooting, portraits, or anything where my subject is stationary, then absolutely I use single-point AF. In this case, the only thing the additional AF points buy you is you can choose one off-center if that's where your subject is, and then you don't need to focus-and-recompose as much. This doesn't matter so much if working from a tripod, where you should use LiveView for contrast detect AF anyway and that's not tied to the AF points.