Since a Colonel wears the Eagle on his collar then, why doesn't the GO ranks an Eagle with a Star and the General wear two beautiful Eagles?

For that answer, you would have to travel back in time and ask the Continental Army as they mirrored their stuff from the British...which was all they really knew...and threw their own twists on the ranks

This inspires more questions.
Why doesn't the Brigadier General command a Brigade?
Anyone else have a hard time distinguishing an old SPC from a LTC and 1-Star since we put rank on the chest?
2 Eagles would look very weird
There could be a lot of rank changes to make things easier to recognize. Real nomenclature for Warrant ranks, more difference between 1SG/SGM/CSM, unique distinction for any command position compared to non command (enlisted and officer), bring back the SPC ranks (there's plenty of use for em)

A good friend made Colonel just before I retired. He said, it’s funny you get promoted to a rank where it matters which direction it goes on your collar and then you get your lobotomy. To that I add, stars don’t have a right or left collar version.

BTW the O6 eagle must face forward on the collar.