It is not because I expect them to need to but because one day they might, and the five minutes it took to show them was free insurance. Practical household knowledge is part of being prepared. It is important to start with your kids early.
My daughter, she's eight, and she can already shut off the main water valve. It took maybe five minutes to show her but now she has that ability for life. It really just shows you how much it pays to start teaching them early.