The National Anthem is the musical symbol of our nation,in both the hearts of Americans and in the minds of people around the world.
"The Star-Spangled Banner" tells the story of soldiers who fought to defend a fort in the War of 1812, as the flag waved above. Meanwhile, "America the Beautiful" is a celebration of all things American. It celebrates our beautiful natural landscapes, our liberty enshrined in law, the blessings of God, those who came before us to create this country, the soldiers who loved country more than life, and the patriot dream that continues to shine bright into the future.
Not to mention, it actually includes the word "America" and it is much easier for average people to sing.