Different world views than you probably have. A person who thinks the USD is stable and the stock market is priced reasonably is going to have a different attitude than one who thinks the USD is going through its riskiest in modern history and that the stock market is looking more and more like an astronomically sized bubble, all with WW3 looming. And then there's the guy in the middle who's just diversifying to try to maximize his gain (or minimize his risk) across all possible outcomes.