Because investors believe that the equity of the company is undervalued compared to the future cash flows. I'm sure plenty of poor investments have been made on

Because investors believe that the equity of the company is undervalued compared to the future cash flows. I'm sure plenty of poor investments have been made on this basis and you can't keep it going forever, but it seems pretty sensible that in some cases a company has great future earning potential without present profits. Especially on a site run by a firm specialising in such investments!