It'll be them that has to clean up the mess!
No, it's not right in the ideal world but if they have no garden, and they both have jobs to go to, then there might be little else they reasonably can do. Arguably, they should have given more thought to owning a dog but it's not the worst thing in the world. As long as the pup has enough water then it'll not come to harm. They'd better take it for a walk once they get home though!
We'll leave ours inside for hours if we're going out and the weather's shite. Or leave her in (as she's getting on now and just sleeps) and put him out in the garden where he can bark at birds to his hearts content!
In total honesty, I don't think people should have dogs in certain circumstances, and can make a good level of commitment to them... but they do and there are greater injustices in the world. And it's only what I think so worth nothing on the scale of things.