The purpose is its way simpler. Even if I (as well as any other players necessary for the process) knew the system perfectly and was making only the correct actions, we'd still be dealing with an overly long process which has to be done in exact order.
First I step down from Gaston, then I wait for my desired lord to step down, then I promote him to lord, then I can become lord of the new region, then I make his city a new duchy. Mind you I haven't gotten to the point yet where I can even see if this works. I may just wind up with some new pitfall in the way.
If I or any other player involved gets even one of these steps out of order the whole process is screwed up and everyone involved has to step down and start over. That's not fun.
