So pocket diapers can be used as covers?
Some people do this. Once you have a "stash" you'd be amazed at all the different ways to stuff, fold, double, etc. Some people use a pocket diaper without an insert as a swim diaper. I just did this the other day when I took my babies swimming. The main thing is that with an AIO or Pocket diaper, the moisture is to be held inside the diaper. If you just use a cover or a pocket as a cover, the pre-fold or doubler would be holding the moisture against the baby. Some people don't like the wetness against the baby. This is also why pre-folds need to be changed more often. I still like them though and don't mind changing out the pre-folds frequently.