Part of it is that when people say the "economy" is up, they're usually only referring to valuations of public companies which is only part of the picture. The price-to-earnings ratio is so wack right now that many companies are trading at 18x their earnings per share, so while profits may be up, the companies are still wildly overvalued compared to their expected output.

Real wage growth has lagged significantly compared to the historical trend. If the labor market continues to take a beating, consumer spending will tank and bring equities down with it.