Because the purpose of a society is to promote a stable, peaceful condition within which people can be safe and prosper. (See: Thomas Hobbes, Leviathan)
To the end that prosperity requires economic forces in order to create opportunities for people to rise disproportionately to their effort, we have a market. But the market serves our society, not vice versa -- the purpose is to control and tame the beast to make it serve us, not to expose ourselves to the wild fluctuations of uncontrolled (or poorly restrained) profit motives. The extent to which market control is reduced raises the bar of informed-ness for all market participants.
In theory we can all be served by an efficient market, if all participants are perfectly informed. In practice, perfect information is unavailable, and lacking that, we will all spend every available minute either seeking information or being duped.
Or: we can sacrifice the goal of theoretical market purity and accept that the rest of us have better things to do with our lives.
To the end that prosperity requires economic forces in order to create opportunities for people to rise disproportionately to their effort, we have a market. But the market serves our society, not vice versa -- the purpose is to control and tame the beast to make it serve us, not to expose ourselves to the wild fluctuations of uncontrolled (or poorly restrained) profit motives. The extent to which market control is reduced raises the bar of informed-ness for all market participants.
In theory we can all be served by an efficient market, if all participants are perfectly informed. In practice, perfect information is unavailable, and lacking that, we will all spend every available minute either seeking information or being duped.
Or: we can sacrifice the goal of theoretical market purity and accept that the rest of us have better things to do with our lives.