I don't know what kind of dogs you had. My dogs never did that. Not my fault if you didn't raise your dog well.
Firstly, my dog(s) never ate his shit, this is about other people's dogs.
Secondly, it's not about raising a dog. Dogs eat their own shit for specific reasons, the food you give them, most of the time is quite high in fat and has a lot of ingredients does not really get digested by it's stomach, so when a dog shits, it obviously still smells a lot of the fat that it ate, hence, will eat it's own shit.
For example, leave your dog next to a cat litter and see what he does, he will eat the cat shit, you know why? Cat food has twice the amount of fat/protein in it than dog food.
So, the idea of raising a dog to not eat his fecal matter, is quite ridiculous on its own when it is in their nature to eat anything with a source of fat. Ask any Vet, they'll tell you the same. I have 2 dogs now, and since I've been 10, I've had another 4. All strays that I have brought in, so trust me, I am more than capable of raising a pet.
Lastly, who cares if dogs have done much for humans, we're talking about which we prefer. You don't get a dog because they're been human helpers at one point or another, you get a pet as a companion. I've had both, and I prefer cats cause they're a lot more independent.
Edit: Oh also, cats have contributed to society, look it up, you'd be quite surprised, and it's been on a global scale; it's called the Black Plague.