Coming on the Jetplane 2

Another question that keep bothers me every time I am on board of a plane is this: Why do they always ask us to adjust our seat to upright position?
I more or less understand about the other plane take off ritual, but I still do not understand why we need to sit upright. I mean, what’s going to happen if the plane takes off and, my gosh, you are sitting with your chair reclined. Are they going to cancel the flight and call the airline security? Or are they going to slap you on the wrist with their plastic fork?
For me, the only reasons that come to my mind are these:
If you put the seat on upright position, it will be easier for the stewardess to see you from the front of the cabin (but that does not make sense, because why do they want to see you? Any eye contact will cause the passengers to ask for water or blankets)
The whole airline industry hates you.

So, for me, the reason we need to sit upright is that the stewardess need to wake up and work all the time, there’s no way they are going to let us sleep and rest, thus they ask us to sit upright in a very uncomfortable position.
But at least that only last until the seatbelt sign if off. Then the stewardess can start banging their food cart to our seat to wake us up.