Because the average age of all those positions have gone up significantly for a single generation. Also a lot of the policy and economic theory that makes up the modern economy were pioneered by boomers like Jack Welch while they were first accumulating power. And there's supplemental evidence such as the projected lifespans of future generations being smaller than the generations before in the first time in modern history.

I'm not claiming just being old automatically makes you greedy, just that if you look at culture the baby boomer generation has implemented policy and an economic attitude that is vastly more selfish than any previous generation.