Reasons why parents are tougher on teenagers than younger kids?

Like the parents makes the 5 year old a sandwich and see how cute he or she is but when the teen asked to make them a sandwich, parents are like, "Who do you think I am? Your maid. Make your own damn sandwich! You're old enough!"
They always ask teens about assignments and being sick you can't always stay home. I rather be 5 again than 15.