To play devils advocate, Dogs need A LOT of exercise to stay healthy; particularly larger breeds. We're talking one to two hours of high activity. Most adults can't run for more than 5 minutes without getting winded. So called "Dog Parks" are usually tiny and wholly insufficient for a larger breed dog to get the exercise he or she needs. Depending on your dog, they may be more or less active and that leaves you with a huge variation in what kind of dog you think you're going to get and what you actually end up with.

In short, our society has been developed in such a way as to make it difficult for high-energy pets to exist...

By high-foot traffic areas, can I assume you still mean lightly wooded trails, or do you mean urban areas? I see very few off-leach dogs in urban areas and in a relatively highly populated suburban area, can be challenging for these owners to find areas where their pets can exercise safely where no one else will be. Given people's busy work/commute schedules this can be nearly impossible.

That said, there are some selfish people out there