Petition One age for everything

There are different ages for everthing. I am referring to things such as driving, sex, drinking, marriage, smoking etc. If there was one universal age for people to do all these things it would be a lot easier to police and would reduce people breaking the law over these sorts of issues. Eighteen would be a good age as that is when you are deemed to be an 'adult'. If everything happened at the same age then people wouldn't want to break the law so much. For example, you can smoke at sixteen but cannot buy cigarettes until you are 18, naturally this is going to make sixteen and seventeen year old smokers try to buy cigarettes or get someone to buy them for them. By having one universal age for all things, it would be more beneficial to everyone.