More than once, I've been put in the position where my dog is getting agitated because they're on leash, their dog can't be controlled because they're off leash, and we're rapidly approaching the "Swift kick or risk injury" stage.
"My dog is off leash because I want them to have freedom" is a profoundly selfish decision if you're in a place to encounter other dogs.
This is cultural, I think. In the UK at least it’s often the norm for dogs to be off leash in open areas like commons (public land, usually grassy or wooded, or a mix of the two), or in other settings where they’re away from roads and won’t encounter livestock.
On public footpaths in the countryside farmers will put up signs indicating where livestock are and where dogs need to be kept on leash. The rest of the time, again, most dogs will be off leash.
Compliance is really high, with almost all dog owners I see following these rules.
There’s a deterrent as well: if your dog is bothering farm animals the farmer is within their rights to shoot the dog.
I do think the post you’re responding to has a very naive view of dog psychology though. Thousands of years of selective breeding means that dogs are fundamentally not wild animals, and as such their behaviours and needs are quite different from their wild relations, such as wolves. Many breeds of dog are so far removed that they would very likely be incapable of surviving in the wild: I’m thinking principally of designer breeds like pugs which, overall, I strongly disapprove of.
Dogs encounter eachother all the time when you're out on a walk and it's... fine (again, I'm talking UK here). What's the worst thing that happens that you're all paranoid about your dog meeting, gasp, the horror... another dog?
This makes no sense to me.
I assure you, even in the uk, dogs are still dogs.
To be fair, I am talking about three or four incidents over twenty years.
[0] To the point where we briefly considered naming a dog Fenton, but then realised the humour would wear off pretty quickly and it wouldn't really be fair on the dog.
...my dog is getting agitated because they're on leash...
