Actor credits on front page of movie entries

The other day, I noticed that the actor who played "Chief" in "One Flew Over the Cuckoos Nest" was not included with the actor list on the front page.  As a significant character in the movie, I thought this was odd.  Today I noticed that the actor who played "Bubba" in "Forest Gump", was also excluded from the front page.  Is this just coincidence, or is there some weird reason not to include these actors on the front pages of the movies they were in?  I am now wondering if other minor characters, who are significant enough to be included with the list of actors on the main imdb pages for movies, who happen to be minorities, are also excluded from the front pages of other movies.