Question about a simple restore

Alright, so I got my replacement iPhone 5 yesterday (my 2nd replacement) and the backup didn't save ALL of my passwords (just some) for my apps.

Is this normal? I don't remember it ever doing this before?

Also, is it because it's a new device? I know when I made backups (with my old phone) and restored (my old phone) all of my passwords were saved..

Any help would be great. Thanks!