People do it, but in my opinion it's highly irresponsible and unfair on the dog.
As for a puppy? No way. It's cruel and will cause all sorts of problems with behaviour (due to boredom), toilet training and separation anxiety. Mine needed letting out to the toilet every 30-60 minutes until he was about five months old. He was toilet trained (as in, he could let us know) but he couldn't hold it for a huge amount of time before having to go.
We have had a dog and we both work but I'm a dog-walker and can take him to work with me. If for whatever reason I can't, my in-laws will look after him for us.
Most of my clients are actually people who can't walk their dogs for some reason - be it age, health issues or a change in circumstances. None of them went out and got a dog and planned to leave it all day.
Today I took two dogs out, aged 4 and 12. Their owners left at 9am, I came in at 11 and took them for a walk, I left at 12.15 and someone will be home by 3pm, so with my break in the middle they are only alone for 4.5 hours or so. They also have a dog flap and each other's company! Plus, the situation where I walk them is only 1-2 times a week, the rest of the time the max. they're left is 3 hours, with a good walk either side.