While wages are obviously a significant factor here, I still wouldn’t be surprised if the primary cause for this is simply the fact that most people aren’t very skilled at managing their personal finances.
I make a pretty decent living, but in discussions with my coworkers who earn as much as I do, and often even more, it becomes apparent that many of them are essentially living from hand to mouth. In contrast, I have a year’s worth of wages invested in stocks and enough cash to purchase two more cars like the one I already own. Finances and saving are subjects I enjoy discussing, but the vast majority of people have zero interest in them, and this has a real impact on their lives.