Big Picture Thesis
Investors who own higher-risk/higher-return assets generate an order of magnitude greater wealth over time than savers who own lower-risk/lower-return assets. (In econo-speak, saving and investing are the same thing, but here "saving" refers to stashing one's money in an asset of stable value and relatively low return like a savings account or certificate of deposit, while "investing" refers to owning assets of fluctuating value but generally higher returns such as stocks or real estate.)
Boomers, on the whole, have demonstrated a greater risk tolerance for investments, while Millennials tend to prefer risk-averse