The thing is OP, dog walkers absolutely have their place, but they're not an adequate replacement for the care of a family. Most of the dogs I walk are on my books for reasons other than full-time working owners.
I have one lady who has developed agoraphobia since getting her dog. Her husband and daughter help out five days a week, but there are two days they can't - which is where I step in. However, that dog is never alone, gets plenty of company and training - the owner just needs help occasionally.
Others don't drive and want their dogs to go to new places where they can run occasionally - so I take their dogs down the beach or to an enclosed field, for example. They get a good run, the company of other dogs and the owner is around the rest of the time.
There's absolutely nothing wrong with employing a dog walker - it's often suggested on threads where the OP has small children and struggles to fit in lunchtime walks around toddlers and newborns, for example. But again, the dog doesn't go home to an empty house - it's just taken out for a while to have a good run about and to give the owners a chance to get other things done.
An hours' walk at lunchtime in between four hour blocks of time alone just isn't enough. It doesn't matter that you can walk them before and after work, you're still going to be leaving your dog alone for 7-8 hours a day at a minimum. Add on things like going to the shops, nights out, childrens' activities, non-dog friendly days out - and the time alone adds up and up.
Just because a dog sleeps all day, doesn't mean that they're happy or content. It often means they're bored and have nothing else to do.