One possibility is that increases in household net worth, though impressive, are just recovering lost ground. People may treat these differently from new gains.
Indeed, by some measures, all the lost ground hasn't been recovered.
Economists at the St. Louis Federal Reserve Bank adjusted the Fed's figures for inflation and population increases since 2007. By this math, average net worth is about 90 percent of its 2007 peak.
For housing alone, the contrast is starker. Consider some numbers.
Prices are up 12 percent over the past year, reports the market-data firm CoreLogic. Still, they're 22 percent below their 2006 peak.
Or take the number of "underwater" homes, with mortgages exceeding their price.
Since late 2009, they've dropped by almost 2.5 million. Good news. But 9.7 million remain. That's almost 20 percent of all homes with a mortgage, says CoreLogic.
Aging may also weaken the wealth effect, says Susan Sterne of Economic Analysis Associates. The more that retirees and near-retirees worry about exhausting their savings, the more cautiously they spend, she argues.
But what really subverted the wealth effect was the financial crisis and Great Recession.
People better appreciate that houses and stocks are risky assets, says economist Paul Edelstein of IHS. They're more reluctant to borrow and spend against them, because today's gains could become tomorrow's losses.
Americans became more defensive, he says. Jobs are scarce; incomes are sluggish. People are not just paying down debt; they're building barriers against hazards they can't foresee.
There has been a stunning shift in behavior, notes Zandi.
In 2006, at the peak of the housing boom, almost 90 percent of homeowners who were refinancing mortgages increased the size of their loans, according to data from Freddie Mac; they were borrowing against higher housing values.
In 2012, 83 percent of refinancing homeowners either didn't change the mortgage amount or lowered it. They were striving to pay off debt.
So the wealth effect varies by time and circumstances. Now it is a casualty of the financial crisis and Great Recession.
We have yet another example of risk aversion dominating the economy.
People eager to borrow have faith in the future; people eager to repay debts worry about the future.
We are prisoners of psychology, which can change but is hard to manipulate. That is the predicament for policy and politics.