Why do some Bibles omit portions of Daniel and Esther?

http://www.catholic.com/quickquestions/how-can-a-story-from-the-book-of-daniel-be-true-if-a-dragon-appears-in-it

Catholic Answers Senior Apologist Jimmy Akin explains why some Bibles omit portions of Daniel and Esther.

Jimmy Akin was born in Texas and grew up nominally Protestant. At age 20 he experienced a profound conversion to Christ. Planning on becoming a Protestant pastor or seminary professor, Jimmy started an intensive study of the Bible, but the more he immersed himself in Scripture, the more he found it to support the Catholic faith. Eventually, he was compelled in conscience to enter the Catholic Church, which he did in 1992. His conversion story, “A Triumph and a Tragedy,” is published in the book Surprised By Truth.

Akin is a Senior Apologist at Catholic Answers, a member on the Catholic Answers Speakers Bureau, a weekly guest on the global radio program, Catholic Answers LIVE, a contributing editor for Catholic Answers Magazine, and the author of numerous publications, including the books Mass Confusion, The Salvation Controversy, The Fathers Know Best, and Mass Revision.