Having read the book Down and Out in Paris and London more than once, and having just finished a review of it, the question of "what is the lesson of this book" comes to mind? 

The poor work long hours and are underpaid. They have nothing but eating, sleeping & working, to fill much of their lives, if they are working, and if they are not, then they have to take charity and when it is found it comes with conditions. At least a thank you is necessary, but often the need to acknowledge that those charity givers are somehow smarter and more deserving needs to be imparted. 

I looked for the overall lesson of the book but found instead this quote by George Orwell.  “It is curious how people take it for granted that they have a right to preach at you and pray over you as soon as your income falls below a certain level.”

A man handing out tickets for the meal inside a place where the homeless were fed was considered to be "one of the good guys", simply based on the fact that he was in a hurry and didn't take any time to convey that he expected the receiver to say "thank you". 

Maybe the message of the book is that even the poor, or maybe especially the poor, have a dignity that has worth.