Why do have I to use SSS Wheight of 1?

[Niyazi.Ertut]

This is a quote from Arnold for maya userguide

Weight

The 'blend' between diffuse and subsurface scattering. When set to 1.0, there is only SSS, and when set to 0 it is only Lambert. In most cases, you want this to be 1.0 (full SSS)."

I'm wondering why it says that it should be 1 in MOST cases. Isn't there any diffuse happening?

to which cases/materials are they referring ?

[Stephen.Blair]

In most cases, like skin, you probably want subsurface scattering, so you use blend = 1

But it's an artistic choice...