Well, answering to your question I'm a SAHM now. I have worked full time years ago but
when I had my full time job, I didn't have dogs yet...so now I've time to walk my dogs.
In Germany (I'm German although living in Spain) workdays are of similar length as in the US,
but as schools for children finish about 14.00h, many children and young people who live at home
take part in walking the dogs. There's mostly somebody at home from the family considering the
many half time jobs of women who have got children and those who are SAHMs.
Another point is that many full time working people, where the couple or single person is out of
house all day, are very reluctant to adopt a dog, knowing that he'll have to stay alone all day
and many Adoption Agencies just don't give dogs to people who are out of house all day long.
In Germany people give much importance to the exercise needs of dogs in general. In Spain
things are very different. Most people don't walk their dogs regularly...they sit in gardens or
terraces and are bored. A minority walks them regularly.