How easily does that material scuff and scratch? Clear stuff looks great new but it does not age well in my opinion. When you have a clear material the idea is to be able to see through it and that can only get worse if you use it. Unless there is a desirable plexiglass patina I'm not aware of =p These seem like the type of knives you'd want to keep pristine.
As far as "utility" I don't know. I guess on the off chance something goes wrong with the internals you could see the problem without having to take it apart? But prior to that you'd be stuck with a scratchy, scuffy looking mess. This is all a long way of saying I think the utility factor is negligible.
Edit:
I suppose I can see some utility for something with more complicated internals (i.e. not a basic folding knife)