There is a few reasons.
The American Gold Eagle is considered legal tender in the United
States with a face value of $50 though the intrinsic value of its
gold content is much higher.
These bullion coins are traded based on the market value for
gold.
The US Gold Eagle can be used in contracts in the USA based on
their $50 face value although they are traded based on the market
rate for gold.
The American Gold Eagle has 1 oz Fine Gold printed in English on
the coin making them highly trustworthy and tradable.
The US Gold Eagle has its 1 oz fine gold content guaranteed by
the United States Government.
The American Gold Eagle is one of the freest trading gold coins
in the world.
US Gold Eagles are 22 Karat gold which gives them a more durable
surface.
The American Gold Eagle is the number one gold coin in North
America.
American Gold Eagles are acceptable for your precious metal
IRA.
The American Gold Eagle is one of the most private investments
there is as Gold Eagles are exempt from IRS 1099B Brokerage
reporting requirements.