Why did many whites call the Creek, Cherokee, Chickasaw, Choctaw, and Seminole groups the
"Five Civilized Tribes"?

  The answer has been explained below

Explanation:

The term civilised tribes was used in the early early federal and colonial period. It referred to the native American nations of the Cherokee, Chocktow, Chicksaw, Seminole and Creek.  

They were called civilised tribes because they had developed economic relations with the whites and also had accepted the american settler culture.  The members of five tribes had adopted European clothing, accepted Christianity, owned slaves and  spoke English.