It sounds like many of you on this forum are very responsable, and you know what you're doing, and you know the needs of your dogs, and you take care of them. High five to you!!!
But, there are some who are so incredibly irresponsable and should never own dogs. In some situations, I feel that it IS cruel to leave a dog alone for many hours at a time.
However, if you already had a dog, and your work situation changed, then that's a different story.
But, if you work 10 hour days, and you get a dog/puppy, that's not right because you already know you won't have a lot of time for the dog.