Why aren’t many successful long term investors that are economists?

hello, as the title says why aren't there professional economists successful in the stock market? I'm not talking for day trading or mid term trading that is mostly gambling, but for long term, value investing (like Buffett etc). Theoretically economists should be able to pick good companies more easily than a professional investor and see where economical trends are going. Also, especially the academics, do you have a portfolio yourself? Are you an active investor or a passive one?