What's the point in 'do not disturb' on the iphone 5?

You're not supposed to get disturbed right? So why in the hell, do the calls still get through?

Notifications>
Do Not Disturb>
Switch off repeated calls

By turning on "do not disturb", all your notifications, messages, calls get silenced.
But if someone calls you twice in less than 3 minutes, the call does go through the second time.
Also, it DOES NOT SILENT the contacts marked as your favourites.
You can find out about it here:
http://support.apple.com/.../kb/HT5463

Only calls repeated within 3 mins are allowed though unless you specify otherwise.