In this novella, the author is trying to depict for us the difficulties of working class life.  She is trying use the story to scold the upper classes for the ways in which they are treating their workers.  This means that she is trying to appeal to the upper classes (who are the main ones reading books for leisure in her time) on an emotional level.  This is the purpose of the rhetorical questions -- to help her engage this audience.

Teachers are encouraged to ask students questions that will get them to think as they listen to a lecture or read a book.  This is what the author is doing here.  The rhetorical questions in this story generally are meant to draw the reader more personally into the story.  They are meant to force the reader to think about the conditions that are faced by the workers.

Look at a few of the rhetorical questions -- they have to do with the conditions the workers face and are meant to get the reader to think about and/or feel these conditions.  For example:

A cloudy day: do you know what that is in a town of iron-works? The skysank down before dawn, muddy, flat, immovable. What do you make of a case like that, amateur psychologist? You call it an altogether serious thing to be alive: to these men it is a drunken jest, a joke,--horrible to angels perhaps, to them commonplace enough.

What if it be stagnant and slimy here? It knows that beyond there waits for it odorous sunlight, quaint old gardens, dusky with soft, green foliage of apple-trees, and flushing crimson with roses,--air, and fields, and mountains.

In each case, the point is to make the reader think and to contrast the lives of the workers with the readers' lives.