It has been the most used translation for most english speaking protestants. There are other Protestant Translations used by non-english speaking Protestants. You also have to remember that Methodists, Baptists and Presbyterians in the USA are major sects formed by English Anglicans who broke with Anglicanism. There are any number of Sects that broke off from them, each on retained the version of the Bible that they originally had when Anglican, but interpreted differently. For many it is because they grew up with it, and while it is a beautiful translation (Elizabethan English) it is what they are accustomed to hearing.