Its not a common sense thing. Thats a slogan not a reality. I'm much more successfull than before and even though I work its not as hard, but that just me. People that are sucessfull sometimes work hard and sometimes they have just figured out how to be more efficient at producing that sucess while others inherit it. Which is why you have things like investments and computers. Efficiency equals sucess not hard work which may mean a lack of efficiency, bad decision making or poor luck.
Your personal experience or what you notice doesn't mean anything when it comes to making generalizations and presenting them to others. Its only used to form your personal opinion and biases. How hard do you think the people work that made the clothes that you wear? You think the people who market them or the receptionist at the corporate office for that company works harder than the person at the sweatshop or the factory in China? No but they get paid a lot more and their qulaity of life is probably much better. Maybe you still consider them more sucessfull. Yes you do have to provide evidence and not just anecdotal evidence but something that actually includes hard workers and lazy ones from all walks of life.
Who works harder and how did you figure that out. Personal experience, because you live everywhere at once and keep statistics?