It's quite deliberate too. Many people use ne theme for work and another for leisure and they define two different themes for those purposes.
You only have to do each theme once and then the phone remebers provided you don;t delete the them from your phone, in which case it forget the settings.
BB do no have any preinstalled themes where the icons are located only on the bottom. The Verizon theme has this, but I prefer the Blackberry L Theme. This gives you icons along the bottom and left side. You're able to get more icons on the home screen this way. If you want to quikly select icons on the left, scroll up or down with the roll mouse. If you want to quikly select icons on the bottom, scroll left or right with the roll mouse.
Posted from my CrackBerry at wapforums.crackberry.com