Markets (like most human systems) aren't really 'supposed' to do anything: they've just kind of evolved as various participants in the market have found them useful for different things, and competition between systems has selected for characteristics that allow them to survive. Economists mostly describe systems, ideas like efficient markets are more of a post-hoc hypothesis for why the system survives, not an up-front designed attribute of the system that was desired when it was set up.
(which basically means that if the conditions mean that the optimal strategy in the market is to basically just run pump-and-dump 'greater-fool' scams on everyone else then that's what you'll see occur)
