Lack of SSS is a big reason why characters in video games often appear "plasticky".
This presentation by one of the developers at EA goes into how the Frostbite 2 engine used in Battlefield 3 approximated translucency for a convincing subsurface scattering look. The effect primarily relies on the thickness of the object and a simple representation of the inner surface diffusion.
Subsurface scattering is used describe the light scattering effect that may occur as the light ray passes through a translucent or semi translucent surface. This scattering effect is oftent times used in video games to create realistic material. In fact, Unreal Engine 4 actually offers a special shading tool called subsurface scattering. It is specifically designed for material interaction involving skin or wax.