Wow, you're about as rude as they come, aren't you?
You assert that I misunderstand the whole concept, while you - of course, understand it perfectly - right?
So if I don't want to be bothered by emails, notifications, my turn on Words With Friends, or text messages while I am busy working using my phone, I guess too bad, huh?
Did you ever once think that this could be useful for when you're using your iPad in a meeting to present material and you don't want your board of directors to see a text from your cousin Jimmy? Or a Skype call from your Aunt Sally? Or a notification from Game Center? Gee, I would call that being DISTURBED while I am BUSY.
Switching it to silent does NOT keep the messages and phone calls from coming thru. It just does not alert thru the speaker. I would still say that I'm being disturbed.
If you feel ok with the current limitations than that is fine for you. But some of us can see the potential for improvement to make this feature more useful.