What are some positive effects of pen names?

They make people want to buy a specific pen depending apon what its called, like if it sounds cool, or if its a brand that you really like in a pencil

Do u mean like when an author changes their name on a book so that they don't have to reveal their identity or an actual name or brand of a pen?, if it's the first one, then some positive effects would be the author could have privacy, a sense of freedom - not being tied to your own name and the feeling of anonymity (being anonymous)