Each newsletter format serves a purpose, and if you are starting one up, you need to be aware that such conventions are in place. You also need to be aware that newsletters are personal and subjective. You are the one who decides what your readers need to know from the information you collect. And your readers count on you to comment on it. It is this subjectivity and personal voice that sets newsletters apart from newspapers and magazines.
Newspapers are by definition objective.
Magazines may take a stand one way or the other but are a collection of opinions and points of view. The newsletter, however, has only one point of view - yours. That gives newsletter publishing a different perspective on the role of advertising as a source of revenue as well. Newspapers and magazines can carry advertising because they are perceived as inherently fair and objective. Newsletters traditionally do not publish ads because everything in the letter, including advertising, implies the editor' s condonation.