"Knowing that risk is on average proportionate to reward, investors like risky strategies, while founders, who don't have a big enough sample size to care what's true on average, tend to be more conservative."

I don't think that's the only reason founders want to keep risk low.

The most important reason is that money has diminishing effect on happiness. People want to be able to guarantee a "moderate" life. What comes beyond that is not as important basic needs.