It's really one of my pet dislikes, but I see it over and over again.
Dog owners with absolutely no control over their animal.
Walking with the leash fully extended (even worse if it's one of those extendable leashes) with the dog almost choking itself to death at the end of it.
Neither the dog nor the owner are getting any enjoyment out of the walk.
The dog is roving at will left and right while other walkers are trying to avoid tripping over the fully extended leash.
Instead of getting the exercise benefit from a nice brisk walk, the owner stops every few seconds while the dog checks out this tree or that lamp post or even this picnic table and then goes through the serious decision of whether or not to pee on it.
I'm often tempted to say "gimme that friggin' lead for 5 minutes and I'll teach your dog how to walk on a leash properly."
I don't, of course. That would be infringing their right to be idiots.
But honestly, it's not that difficult to train your dog. And yourself in the process. You'll both be much happier.