Most parents want to leave their kids something, but if the kids are successful, it's not really necessary.
@Walt is correct that money buried in the backyard loses value over time, but if, as in my case, a person doesn't expect to live more than 15 years, then that becomes a more manageable calculation.
Between the Housing/Banking/Great Recession 15 years ago to Trump's fucking up the economy today, cumulative inflation has been almost 50%. What cost $1 in 2010 costs $1.50 today.
https://www.usinflationcalculator.com/
Three other factors besides Stocks/401Ks/etc to consider are owning one's own home/property, pensions, and inheritances/outliving all your relatives. The same question I ask of the Oligarchs applies to everyone else: "How much money do you need to live comfortably for the rest of your life?"
As it is, my wife and I are fortunate to be comfortable. I don't need to follow the market since most of our financial investments are in stable areas that keep up with average inflation albeit not "investing for the future".