Lowering the age of majority will act as a panacea for all. When you lower the age where some one can have sex with a legal adult, that will be a gate way for many other unsavory things to happen, like the lowering of the drinking age and lowering of the age to buy cigarettes.
There are currently many issues with minorities and certain aspects of life which require you to be either 18 years or older, or 21 years or older. Drinking is a huge example of this. Young men and women dont fully understand the consequences of their actions while drinking and may, at times, cause unlawful circumstances that affect others.