Question About Paperbag Albums

This is truly a curious question because I don't really see the point.

Why do you use paperbags when you are going to cover it with pretty papers? Isn't the point of using the material is to explore and expose its own properties and make it pretty without covering it with other types of paper unless, maybe, you're collaging on it? I mean, why call it paperbag album if you can't see the paperbag?

I don't understand. Honestly, if it is just utilizing paperbags as another material and it isn't being called paperbag album, I won't be asking this question.