Good questions, here are some more.
Why does the sun lighten our hair, but darken our skin?
Why can't women put on mascara with their mouth closed?
Why doesn't glue stick to the inside of the bottle?
Why don't you ever see the headline "Psychic Wins Lottery"?
Why is "abbreviated" such a long word?
Why is a boxing ring square?
Why is it called lipstick if you can still move your lips?
Why is it considered necessary to nail down the lid of a coffin?
Why is it that doctors call what they do "practice"?
Why is it that rain drops but snow falls?
Why is it that to stop Windows 95 or 98, you have to click on "Start"?
Why is it that when you're driving and looking for an address, you turn down the volume on the radio?
Why is lemon juice made with artificial flavour, and dishwashing liquid is made with real lemons?
Why is the man who invests all your money called a broker?
Why is the third hand on the watch called a second hand?
Why is the time of day with the slowest traffic called rush hour?
Why is the word dictionary in the dictionary?
Why isn't there a special name for the tops of your feet?
You know that little indestructible black box that is used on planes? Why can't they make the whole plane out of the same substance?
Why do you need a driver's license to buy booze when you can't drink and drive?
Why isn't there mouse-flavoured cat food?
Why did kamakazi pilots wear crash helmets?