There are many reason the people could have wanted the law (or amendment) changed. Many feel that those at 18 and possibly 19 and 20 are too young to make a vital decision such as that of voting for President. People still view them as children making it hard for people to accept this law (or amendment). At the time, as stated, 18 and 19 year olds were being drafted for war. If these children were old enough to fight in the wars then these children were old enough to help make decisions for their country. They made this law (or amendment) so these young men could help take part in history, not only as a soldier but a voter too. I hole this help you. Best of luck!