Because I am assuring myself that I made the right choice. Also you forgot to mention the price variation for the length of the cable.
Also I can see some companies "tailor" their cables to make them look high end for example Monster. This makes the cables seem more appealing to other people because they look high tech. That gives them another reason to sell them at a higher price. So some people might buy the more expensive cables because they want their setups to match and look good.
But either way I can see your opinion on the subject. Many people have their own preferences. Some people have deeper pockets than others too.