@GT
I know your point of view.. but let's take it a step further.. The ultimate goal of a cast is a hollow shape for giants.
Developmentally, the drilling of the hollow shape is designed to maintain that body shape through motion. Yes, you need to pass through the arch phase to cast up. However, for any skill out of the cast (a non-skill, mind you, and if you think of it, it's technically a free swing), a hollow shape needs to be re-enforced. Be it a free-hip, front giant, back giant, or a release move, a hollow is the foundation for almost all elements that come from a cast.
For young girls, some skills need to be "made up" to accomodate for their lack of development. That's why glides are an element at level 4 (kip) and front hip circles (be it for a weiler or just learning to get yourself away from the bar while circling)... A cast to hollow is a good benchmark to see how well a child is progressing towards a future skill, as well as giving them a current goal that is credited and merited.
Your argument is valid. It's an archy skill. However, it also separates a good gymnast from a great one. Our sport is, partially, based in aestetics. A straight body cast is, by all means, more pleasing to the eye than an archy one. It also makes for an easier transition towards future skills.
Again, this is just one opinion...
@Tracy -
Break down the motion for them, and work on static holds. Help them feel confident in the positions you want them to pass and work through. It's like any other skill. Break it down to its root components, and they will understand what it feels like before ever actually attempting. They need to feel the little successes before feeling the whole. The suggestions above are great examples!
Good luck
