I'd like to give a bit of historical background. (Note: The following is very simplified. However, I don't feel like writing a book.)
In the 1800s, the industrialized world was divided into three economic groups. There were the tiny minority of the rich (either capitalists or large landowners). There was the somewhat larger middle class (aka bourgeoisie) of managers, professional people and merchants. Finally there was the huge group of workers (aka lumpen proliteriat, downtrodden masses, etc.). The rich were quite well off, the middle class lived comfortably, and the workers lived a hand to mouth existence where life was "squalid, brutish and short."
Laissez faire capitalism was the economic system of the day. One of the tenets of this system was that everyone was responsible only for himself. John Stuart Mill's concept of the Social Contract was considered meaningless because, theoretically, anyone could achieve any position they wanted and were willing to work for. In real life, while there was a very limited upward mobility, the vast majority of people stayed in the social/economic class they were born into.
The Scotsman Keir Hardie, a founder of the British Labour Party and one of the few workers to become politically active, was a 15 year old factory worker who was fired because he was 10 minutes late for his job. He also forfeited his week's pay "to teach him a lesson." This was not only legal, it wasn't uncommon. Because of abuses like this, movements like socialism, anarchy and socialism's off-shoot, Marxism, had a great deal of appeal to many workers and to bourgeois supporters. Prince Peter Kropotkin, a major anarchist philosopher, worked to bring about economic and social change.
The changes that socialism, etc. were trying to achieve can be summed up in the phrases "social justice" and Marx's "from each according to his ability, to each according to his needs." By WWI many of these changes did happen in Western countries but through political means, not by revolution. Laissez faire capitalism was replaced by various forms of governmental intervention, including minimum wage, child labor laws, work safety laws, and the like. However, for some, this intervention did not go far enough, and The Revolution was still sought.