Aside from the insider trading comment another user made, with which I agree:
Material information ought to be accessible by all investors in a fair and orderly way. This is the same reason that stocks get halted for impending news intraday, and earnings reports are released outside of regular trading hours (except perhaps for ADRs and other multi-market securities). Scheduled injections of information make it easier for market participants of varying sizes and geographies to receive and digest information at parity with one another.
Material information ought to be accessible by all investors in a fair and orderly way. This is the same reason that stocks get halted for impending news intraday, and earnings reports are released outside of regular trading hours (except perhaps for ADRs and other multi-market securities). Scheduled injections of information make it easier for market participants of varying sizes and geographies to receive and digest information at parity with one another.