@BillRM,
Well, sure. Instead of turning the key and going, you've got to catch the horse, get a bridle in it's mouth, throw on a saddle blanket and saddle, and get on it. Get to work and park the horse and hope it doesn't get too hungry. Ride it home, unsaddle it, groom it, and feed it. All the while, it's been leaving a trail of horse pucky all across town, drawing flies and what not till somebody comes by with a wagon and shovel.