Well, I know I'm new here but I still wanted to add my two cence in.
I don't have much to add to what has already been previously said by many, all of which I agree with. All I have is personal experience.
At our house we don't have a fence, nor do we plan on ever getting one. We live in a small little group of houses in the middle of town where we are close to our neighbors and a fence would really truly limit the amount of interaction that we would have with them. Instead we have a long zip line with a rope on it that give the dogs a lot of place to run.
I have three dogs right now, one 5 year old female, one 14 year old male and one 5 month old puppy. Hannah, the five year old female doesn't like to be outside unless she is getting direct interaction with someone or they are sitting out there when she is out, and even then she would much rather be inside on the couch. The puppy of course isn't outside by herself yet. But Rascal, our 14 year old male loves nothing more than being outside on the lead sleeping in the grass.
In the summer he's out on his lead for hours at a time, typically, depending on the heat, for at most 14ish hours a day. He has water and gets fed out there and my dad will a lot of times sit on our deck while he's out there. Rascal (and the other dogs) have the option to go in at all times, the lead reaches the door to our house which they can push open and do push open when they feel like it. But he doesn't do that very often. He loves it outside on his rope basking in the sun.
He doesn't really go on walks, he's old with arthritis, half blind and deaf. But he does love to be outside. If we had a fence in yard he would do the exact thing he does now, lay down and sleep.
Hannah while not a fan of being a lone outside also likes to lie there in the summer and sleep and/or play with Rascal. She will normally be out there for a few hours everyday.
My dogs, in my opinion are better taken care of than many dogs I see that aren't tethered or restrained with some kind of rope/chain etc. Would I like to have a fence? Of course I would, but do I think not having one makes me a bad dog owner? Not in the least, I think it makes me responsible enough to figure out a safe alternative to a fence that keeps my dogs happy.
As was said, fences are not cheap and when you begin to make decrees that every dog owner should have one you make dog ownership very elitist. Instead of making blanket statements that are proved false repeatedly why not look at how the dog is physically and mentally?
Not every tethered dog is an unhappy/neglected dog and not every unhappy/neglected dog is a tethered dog.