Why did Edward stratemeyer have pen names?

A pen name may be used to make the author's name more distinctive, to disguise his or her gender, to distance an author from some or all of his or her works, to protect the author from retribution for his or her writings, or for any of a number of reasons related to the marketing or aesthetic presentation of the work. The author's name may be known only to the publisher, or may come to be common knowledge.