This is my theory.
In an ideal world, Apple wouldn't have settings for such tasks.
They don't want people thinking about turning WiFi, 3G... etc on or off to manage battery or other things.
Ideally the software would manage these in a more effective way.
For example, when away from Wifi it puts any Wifi hardware into a low power 'sleep' state.
I think by making these settings much more visable, it opens them up to be 'played' with more often by more people, when in actual fact Apple doesn't want people worrying about such things.
I think the new "Use 3G when WiFi is weak" setting is a good indicator of this.
Maybe i'm conmpletely wrong, and in IOS7 we'll see toggles... but it's just my theory.