That's a great metaphor, Eddy. You're right. I've never seen a dog who didn't love a walk. But, those glum humans walking their dogs aren't sad because they wish they were dead. They're sad because sometimes walking the dog is drudgery, like washing the dishes, or trimming your toenails. When I was a pre-teen, and had to walk the family dog, even though I loved that dog, I didn't enjoy walking her. There were 85 things I would have enjoyed doing more. Then, when I was older, I dog sat for my cousin for a week. I had been dogless for few years. But, for the first time ever, I enjoyed walking him. I've had my dog for almost ten years now, and I LOVE walking him. He's the best company, always up for fun. If I want to sprint up a steep hill, he's into it. If I want to walk him at 2 o'clock in the morning, through the snow, he loves it. Just walking, running, sniffing everything seems to be what he lives for, and I love that I can do that with him because it makes me feel better, too.
I'll bet you a 1000 buck$ that if you asked 10 of those "glum" dog owners if they're glad to be alive, and they were honest, at least 8 of them would say yes. And one smart asss would probably say, "the alternative is worse." Try it sometime. Ask friends, and see what they say. I think you'll be surprised how uniform the answers will be. Take care.