Why Body mesh under clothes?

[NordicRunes]

Why do some clothes have their own body mesh included in the .nif?

I want to make skin-thight armors for the arms, but there is clipping with the body mesh of the torso outfit.

So, why include it, and maybe, how can I fix my clipping without breaking anything mesh-wise?

[mac2636]

I use it so it replaces the default mesh to avoid clipping. By including a ref mesh and using zap sliders you can almost completely eliminate clipping (except around the neck area sometimes).