Necessity isn't always the mother of invention.
Consider the Dog Powered Scooter, a kooky contraption that involves strapping your dog into a rig attached to your scooter or bike. You still control the steering (otherwise, dog will inevitably lead you to squirrels and other dogs) but the dog does most of the work.
If you are into the idea, this probably means you are lazy.
The brain pup of Oregon-based Mark Schuette is similar to sledding only to the extent that dogs (up to four) double as a motor. But in this case, they are positioned slightly behind the vehicle, not in front of it. Also, unlike sledding, you can do it in the summer on a bike path; just be prepared for an onslaught of stink eye. You can read more about how it works here (warning: the writing contains several typos and the All Caps text reads like an over-caffeinated instructional). And in fact, it may even be that "practical urban mushing" (as Schuette calls it) requires the owner to work in tandem with dog.
Defenders (perhaps the ones that have uploaded videos to YouTube ) might insist that dogs like and need activity. They might also maintain that the scooter rigging isn't all that different from a leash, the main difference being that the dogs are now forced to pick up the pace.
Still, is riding a scooter so boring that people would prefer to delegate the physical exertion to their dogs?
Schuette insists on his site that the rigging is safe and comfortable for the dogs (there's shock absorbent padding) but he lists several safety precautions including this one: "These units are not recommended for couch potato or overly spooky dogs." [sic] Poor spooky dogs.
Now that he has sold "hundreds of DogPowered units in use around the world," Schuette notes that he is working on making the device compatible with other animals. Because a wild boar-powered scooter would be a great follow up, wouldn't it?