-The 90's was, after all, only about 10 years ago and the memory of most investors is not quite that short term-- esp. after getting a financial hosing.
-There are new, younger investors today who were maybe little more than teenagers in the 90's. While these new investors did not actually experience the bubble/burst they do know of it; perhaps even through the stock market troubles of their immediate family.
- The situations -- politically, world, national, social, in business, et. al. is not what it was ten years ago. This too will effect investors.
-And last but not least is that fact that (we) boomers are 10 years closer to retirement than in the 90's. That alone is a mighty darn factor.
...Because when peoples' stock portfolios go up, they feel richer and spend more, which creates more jobs.
Actually, more people "feel richer and spend more" not b/c of their stock porfolio but because of the new-thanks-to-low-interest-rates equity in their houses. They can refinance, pay less every month, and the the "left over" money go out and buy/invest in things.