The problem is that this would make the company too responsive to the needs of investors rather than its markets.
The corporations power is delegated via its shares but its value is derived from the markets it serves. It’s in the interest of shareholders (who passively invest in it) for the corporation to judge projects based on what the markets think are valuable. Neither the corporation nor the shareholders know exactly what that may be, but the corporation spends more time and effort trying to get a good answer than the shareholders do. So the shareholders leave everything beyond the most drastic decisions (sell, close the company etc) to the corporation.