I think the problem with going to a more advanced rigging system, is that all current content would no longer work, unless they bloat the application to accomodate two separate rigging systems, the old, and a newer type.

Imagine the hue and cry in the forums if all previous rigged content no longer worked, and the abuse they would take if only the new human figures worked.

Or if suddenly the application ate a ton more memory, because it had to accomodate both rigging systems.

Way too many people take way too many things way too seriously.