I knew my truck did and that friends with various other vehicles have them to.
As far as i can tell, it's more of a warranty thing or rather "get out of a warranty repair" thing.
The technician at the dealership can tell how fast and hard you drive, if your oil was way too old or low, if you were driving too fast, using bad gas, etc.....so push come to shove, "that" repair isn't covered by warranty after all so cough up some $$$ buddy!
Not all of the computers are the same, though. Only certain information is retained. On Heavy service vehicles, they keep much more detailed records, like that gas quality log, the speed logs, braking, and engine hours. Light Duty vehicles usually record warnings, oil change intervals, and the likes. I also wonder just how much storage space a computer like this has. As the vehicles aren't routinely accessed, after a certain number of years, the vehicles black boxes have to be filled as to retained information.
Mine has one and it's fun to tap into it to see what's being recorded. I use a wi-fi dongle that I plug into the ODB II port and use software on a tablet to read all the info in realtime. They record everything you can imagine, now I can too.