Question below is about a scene from eddie murphy's raw movie?

In the first scene when young eddie murphy tells a joke in front of his family at the gathering. Samuel l jackson who plays his uncle is the only one who finds it funny he says " I love that doodoo line that boys got talent". But my question is why was the mother and father and the rest of the family looking so serious and why did the mom and dad look at eachother with a terrified look on their face??