For one, you could do a lot of intense animation work externally in Max or Maya, where you can have better control over things like cloth simulation. For example, if you had a character get out of bed and you want the blanket on top to move appropriately, then the character grabs the blanket and drags it off the bed. This would be a rather complex cloth sim and would probably require some manual tweaking on top of the simulation. Forget about trying to do this with a series of morph targets. On the other hand, you could export the vertex animation (large files for something this complex) and you’d be all set.
-S