This is a fascinating topic, which really gets to the heart of my own field of study, as honor is a central underpinning of dueling. I don't have too much material written which deals specifically with the decline of honor as a central organizing principle in society, but I do discuss a fair bit about how honor related to life, especially for elite men in Western society in the previous discussions of dueling I have written. The one which I think can speak the most to what you are asking would be this response in the Hamilton AMA, which discusses the importance of honor and reputation in politics during the Early Republic, when personal status was a substitute for weak party structures. Again, somewhat tangential to the heart of your question, but nevertheless I hope illustrative of how things were different in the 19th century.

What a complicated question.....

This is a question that might be better suited to anthropology or sociology. Nevertheless I'm going to give it a shot homie, but I think my answer is going to be too long to interest many people.

I'm going to try and answer this from a war perspective.

Zygmunt Bauman would probably argue that the rise of complex modern civilization changed the concept of honor as the results of ones actions becoming morally and physically disconnected. In Modernity and the Holocaust he mentions the rise of artillery, where the action (firing artillery) is physically removed from the result (a bunch of dead people) in a way that is radically different than previous warfare. Now, yes, one could make an argument that he is incorrect, that artillery is not THAT BIG of a leap from say slingers that xenophon describes or mounted Mongolian horse archers under the Khans, but the important thing is to see it as part of a process. We can not compare drone strikes to Persian arrows in terms of honor.

We all remember Captain John Yossarian in Joseph Heller's Catch 22. Well, what was his big problem as a World War Two pilot? Bombing people that he would never see and that had done nothing to him. He saw this as insane and, if you could ask a fictional character I am sure he would also state, lacking in honor.

Now lets move back 100 years or so from the 1940s to the 1840s. Mikhail Lermontov's novella, A Hero of Our Time, not only starts off 70 years of great Russian writers, but also introduces us to Grigory Alexandrovich Pechorin. One could argue about if Pechorin is an honorable man or not, but the concept of honor in the stories is very clear. So what happened between the 1840s and the 1940s to change the concept of honor?

Well, broadly speaking, society got much more complex. Now ones actions are very disconnected from the results and morally one does not need to take responsibility for immoral actions. This is true for two reasons. First, we don't see the results, for example when one buys a smartphone there is a process involving African labor for precious metals and Chinese labor for construction that we don't see. Now take this times 100 and we have our current day morality, one downloads a movie, eats salmon or buys a book by Henry Kissinger and never sees directly the environmental or social impact and thus never has to ethically question their own ideas of honor. Secondly, our moral compass comes from the nation state and the authority of the administration in whatever organization we work for. One can not compare the Enron scandal to the Scottish colonization of panama or the Holocaust to Alexander the Great destroying Thebes. The first are clearly products of modern society and bureaucracy.

Sorry for the digression. So in terms of society getting more complex, the big change between Pechorin and Yossarian was the Great War. This event MUST be seen in terms of a logical and rational extension of modern western civilization. It is also going to be the dying breath of honor. The system was based on bureaucracy, not honor, the (false) idea of the honor of the Battle of Thermopylae is not going to work in 1916 when you need to logistical capabilities to launch the Somme. Sure it might work to motivate the troops at the time, but as the French and German military mutinies or the British in the 1920s and 30s show, one is cashing in all their chips so to speak. We also should remember the anti-war poets of the First World War, these poets are the ones we remember, not the romantic poets who spoke of honor. Not many people today are reading I Have a Rendezvous with Death by Alan Seeger.

In chapter 7 of Modernity and the Holocaust, Towards a Sociological Theory of Morality, Bauman states: powerful moral drives have a pre-societal origin, while some aspects of modern societal organization cause considerable weakening of their constraining power; that, in effect, society may make the immoral conduct more, rather than less, plausible and the self-legitimizing need of modern bureaucracy which set to destroy the competition of norms deriving from drives and proclivities it (does) not control (pp 198). Basically what Bauman is getting at is that we get our moral compass, or honor if you will, from the bureaucracy around us and the authority it derives from the modern nation state. It is why police can act in an unethical manner, because they are just following the rules, its why accountants at Arthur Anderson can cover for Enron, its why the military can make the highway of death in the first gulf war, its why if a boss asks you to do something dishonorable a large number of people will.

Basically, modern society is too complex for a societal wide system of honor beyond something like not hitting women in public. Even if it was not a concept of honor is threatening to the government (administration/education/police/military/healthcare etc I am not just talking about the politicians) and to the large companies that many people work for.

I hope this helps.