On Financial Statments and Human Nature

It occurs to me as I read Babson College's Preparatory Material regarding financial statements, that it is much easier to organize information that is in your favor, that is to say, that doesn't indicate poor performance.  Regarding how to present finances, I wonder why there isn't just a single standard to not allow any variation in how these crucial numbers are reported.  With a single standard, every company would be on an even playing field and "ethical deviations" would be easier to spot.