Dogs without a Leash

I viewed something nice the other day coming from Wholefoods: an unleashed dog walking next to its master with its tail up and exhuberant confident energy. How nice! I would not want to be leashed if I was a dog, would you?... It is totally unfair to the dog.

I read that dogs on a leash tend to experience high levels of frustration because "the leash unable them to express normal canine body language and interact with other dogs normally". By nature dogs are "motivated to greet one another", but on a leash they can' t do that (https://www.sfspca.org/sites/default/files/dog_behavior_dog-dog_aggression_on_leash.pdf)

I get it, in the city, with buzzing cars on every direction, the dog's owner will get highly anxious on letting their dogs walking unleashed on the side walk. But occasionally... it might happen.

When I was in Guanajuato, Mexico, last year, during the Cervantino Festival, one of their busier seasons of the year, I saw several unleashed dogs walking next to their owners, jumping to greet everyone that came their way, but always maintaining its course. People responded to the dog with tender words, a smile, and sometimes with a caress. Uhm... would that friendly response happen in USA?...