Another wrinkle I didn't see below is that there are lots of people who really go through a lot of effort to not think about things. As an old colleague used to put it, "You've got all the numbers, you're just not doing the math."
It's just easier to keep doing what you're doing, plugging along, rather than consider that there might be a problem. That's hard itself, but if there IS a problem, you'll have to solve it and change. Too hard. So don't think.