As long as the couple know that the type of dog can sustain long periods of inactivity in the house or cage, then I don't see a problem with a working couple owning a puppy/dog.
For example my family owns a miniature New York terrier and we choose this type of dog because we knew that any pet we get would constantly be subjected to long periods of containment.
Me and my husband both work and we have a puppy. He is an extremely well behaved puppy and I think he will grow into a fine dog. I take him on two walks a days as that's all I can do till he is older and he has his 3 meals, he is so spoilt and gets so much love and attention!
I don't understand why there is so much hate for people who work and have dogs. How do they expect people to pay for them if they don't work? He has had all his vaccinations, chipped, has the best food, lots of toys. If we didn't work we wouldn't be able to afford to give him all this!
If it was just rich families who don't need to work that had dogs then there would be thousands of them in kennels and on the streets.
I think if you can still give a puppy/dog the love, attention and exercise it needs and can still work then there is no problem.
Who would take care for the puppy/dog. How would it get fed. Who would train and play with the puppy/dog. Who would clean and groom it. Who would take it for walks or to a dog park. Who would let him get fresh air and for it to be able to do it's own dung or liquids. What about the right amount of attention.
Dog is a great responsibility, not to mention a puppy that needs constant supervision, and i don't even include dog training into this argument. Puppy is still a kid, leaving a puppy alone at home is cruel. You can't just put water, a feeder and just later clean the mess he is going to make.
The little puppy would get no love from it's owners if both partners worked full time. For the dog those 7-10 hrs on average would be a long time to wait to play and potty. If you have a smaller dog you would have to go back to home at your lunch break to let him out to pee. It would not be great for the owners and puppy but is possible.
A puppy needs a lot of attention and care to grow up to be a well trained dog. Bigger puppies or certain breeds need more exercise and human interaction, even as dogs.
An adult dog is more suitable, since it is trained.
However, an adult or dog, it does depend on the hours the couple works. If it is a 9-5 job 5 days a week, the dog should be fine as long as it gets properly treated and cared for once the couple is home. If it is a 7-5 job, plus driving 45 minutes there and back, then that is a problem. Dogs are meant to be cared for and loved. If you can't be there for the dog and give it the affection it deserves, you might as well not get one at all.