That's a good point. Also, the valve is easy to turn off using a pair of ChannelLocks, and that way you get to stick your arm down inside the box and get acquainted with the local wildlife.He asked me if I had one of the tools to operate the shutoff and I said nope. He went on to say that he gives one ($12 at your favorite big box home improvement store) to all of his friends as a housewarming present. He tells them to hang it on their garage wall in a convenient place and shows them how to use it. Said that many friends have thanked him later.
More importantly, I think every adult in the house and kids old enough to be at home alone should know how to shut off the water, the gas, and the electricity. It could save thousands of dollars in repair bills and a lot of trouble. When that pipe bursts inside the wall, it's no time to realize you don't know where the main shutoff is located.
Water: If you've got city water, the shutoff valve is usually outside by the curb in a box where you water meter is. As manual meter readers go the way of the dinosaur, these boxes tend to get overgrown by plantings or buried--it's worth the trouble to keep yours accessible.
If you have a well, there'll be a shutoff valve somewhere on the main line. If you can't find it, shut off power to the pump and you'll just have to wait until the water in the pressure tank drains out.
Electricity: Usually a big breaker at the top (or bottom) of the circuit breaker panel. Sometimes there's another big breaker outside the house underneath the electric meter.
Natural Gas: Usually at the gas meter.
For water or gas: Grab the small flat valve handle with pliers or a wrench and twist it 90 degrees (whichever way it will go) until it "crosses" the pipe. It should be off then.