Also, many erstwhile stock investors have settled comfortably into bonds in recent years. They're content to accept the historically lower returns from fixed income in place of the volatility inherent in stocks.
Bonds have produced exceptionally strong gains in recent years. In addition to pocketing interest payments, investors have benefited as falling interest rates have increased the underlying value of their securities.
The risk is that the process could reverse as interest rates rise, which many experts believe will happen in coming years as the economy improves.
That could deal an unexpected blow to investors who thought they were being cautious.
Experts also worry about a potential small-investor backlash if stocks slip into even a modest tailspin.
The Dow has climbed nearly 12% from mid-November and in a virtual straight line up in January. Based on history, it would be normal for share prices to give back some of their gains before resuming their advance.
"If you missed it, this might not be the right time to jump into [the market] because it's done so well," Hsu said. "People were not invested in equities when they were cheap and could be opportunistic, and they pay attention only after equities have done very well."