Why isnt palindrome spelled the same way backwards?

Why is it that when you transport something by car, its called a shipment, but when you transport something by ship, its called cargo?

You know that little indestructible black box that is used on planes, why cant they make the whole plane out of the same substance?

Why is it that when youre driving and looking for an address, you turn down the volume on the radio?

If you have your finger touching the rearview mirror that says — objects in mirror are closer than they appear, how can that be possible?