As others have said, they're faster than most things through town and also handy for chasing scrotes illegally riding dirt bikes on fields/in parks, particularly if a helicopter isn't available.
London police were looking at using them a couple of years ago. I'm not sure if they ever did or not, but I've never seen a policeman "patroling" on one. Doesn't quite have the "all day in the saddle" comfort of a pan, does it?
