There have been experiments with clothifying skin - see Poser Soft Bodies by RajDArge in the tutorials section for example (I can't work out how to link to it).

But the difference between cloth and skin is that skin doesn't have consistent characteristics across the surface of a body - how it reacts will depend on skeleton structure, muscle density and all sorts of factors that I, as a layman untrained in anatomy, can only guess at. To be realistic, all these factors would need to be programmed in to a simulate-able figure.

I look forward to having this feature, sure. To be able to bend an elbow or knee and have the flesh compress in a realistic way, or to have tight clothing behave in a proper two-way interaction with skin, would be great. It will happen eventually. I'm not holding my breath though. ;)