Just watched Harry's Practice and there was a lady who took her dog to the park in a Pram.
It was because the dog had a fear of walking there, because of other dogs and being scared of them.
Once at the park, the dog ran around (out of the pram). Those little dogs can be very troublesome, I know.
There is also a really old lady in town here, that prams her dog to the park, then lets it free run. She must be around 90 - but every day, she pushes that dog to the park, to let it have a run. More control than a leash for her frail body.
So, maybe it that the Dogs in Prams are just taken to a Park, like in a car, to be let off the leash?