I am new to gymnastics, but a veteran to cheerleading and I know for a fact that the judges DEFINITELY DO NOT score the routine as high if the girls are not smiling. Psychologically speaking, when you smile at someone that person's natural reaction is to smile back and this produces endorphins which make you feel good...so with this logic it may make the judges feel better about the routine thus resulting in higher scores. Also, when the athlete smiles, it looks like that athlete is having a good time and ENJOYING herself. In cheerleading, the routines where the kids have tons of energy and are smiling and generally look like they are having a great time generally score higher.
My daughter's cheer team came in 2nd place by only TWO ONE HUNDREDTHS of a point (.02) at the NCA National Championships in Dallas TX in February and the reason according to the score sheets was "Not enough energy, looked a bit scared, and You SEEMED to have more energy yesterday". We had no deductions whatsoever, but the final score was based on the girls facials (smiling or not enough smiling). Cheerleading and gymnastics can be both very subjective and skill alone can not always guarantee a win.
So...the moral of the story is--SMILE!!!!!!
Kat