He was in quite a bit of the stories, I guess he just wasn't noticed as much. That could be taken as a good thing or as a bad thing depending on how you look at it.
"Franklin sits in front of Peppermint Patty in school, revealed November 12, 1969, and is the center fielder of her baseball team. Franklin acts as a thoughtful counterpart to Linus, and is as adept at quoting the Old Testament as Linus is. One connection that Franklin and Charlie Brown have is their mutual interest in their grandfathers; with Franklin describing his as energetic and content with his age with the motto, "When you're over the hill, you pick up speed." Franklin has few anxieties or obsessions and the novelty of his racial background has long since faded. In Race for Your Life, Charlie Brown, Franklin is among the other children who must deal with culture shock of transitioning from his nice neighborhood back home to living in a Spartan summer camp in the Western United States, and learning that they will wake every morning at 5 A.M. In It's Flashbeagle, Charlie Brown, Franklin is shown to be a fan of disco dancing and breakdancing, and frequented a discothèque with Snoopy. He is also quite knowledgeable about jazz music and plays Scott Joplin's "Maple Leaf Rag" in the "Music and Heroes of America" episode of This Is America, Charlie Brown, which aired May 23, 1989."