If someone knows what they are getting themselves into they may even wind up hurting themselves but it's different because they knew what they were getting themselves into. If someone is made to go through a class that highlights all the dangers and then pass a test on it they're aware of the dangers. If they decide not to care then that's on them. If they decide not to care in a way that puts others at risk (i.E. Drinking and driving) then they get to go to jail and the privilege should at least for a time be revoked.
Some of the age restriction rules like drinking or smoking are based off of scientific studies of the brain. It is shown that drinking and smoking deteriorates the brain and people of a young age should not be allowed to do these things because it would severely damage their still developing brain. However a combination of age restrictions and competency restrictions would be a good idea.
There are some things that should have both age and competency restrictions and some that shouldn't. Technically we already have it set up with your license. You have to pass a test and be of a certain age to get your license. So you have to show age and competency.
In general, age restrictions should be replaced with competency restrictions. This is definitely the case when it comes to driving. An older person who can see and hear well, and has no illness that would affect their driving, should be allowed to drive at any age. There are very few situations where age restriction is necessary.
Age restrictions should most definitely be replaced with competency restrictions. For example, there are some elderly people who are more than capable of driving a motor vehicle safely and effectively, and there are some non-elderly people who are not inherently capable of driving a motorized vehicle safely and effectively. Changing the restrictions would fix this oversight.
If a 14-year-old is competent enough to drive, work and go to school, then so be it. Some children enter college in their early teens after passing a GED. A one-size-fits-all age category simply doesn't make sense. If this restriction will be changed, the only difficulty is determining an age to become a liberated adult. Can a 14 year-old live on his or her own with a full-time job, or does that person still need parental permission?
People should gain adult privileges such as signing contracts, voting, moving out, drinking, smoking and consenting to medical care when they demonstrate certain cognitive abilities which will be independent judgment and foresight skills. If they don't have such abilities they will be considered "incompetent" and will be denied such privileges. A short, simple, unbiased, accurate and fool-proof competency assessment should be available as a safe measure and once people reach a certain age they should be required to take a competency assessment (I'm thinking that age should be 14).
I believe it would be too difficult to measure competency levels in people in order to replace restrictions currently based on age. I believe it would become an incredible complicated system that would be impossible to govern. I think age restrictions are used as a basis for competency and it is far less complicated to do it that way.
How would you assess competency? How would you assess a person's ability to make a decision for themselves as opposed to someone else making it for them? We'd all love to ensure that the "right" people have access and the "wrong" people don't to things that we view as dangerous, but there's no good way to separate the groups.
This would be too hard to regulate and would have too many people looking for ways to get around it. With age restrictions, you have something black and white in place to determine if people are ready for something or not. It's far from perfect, but at least it isn't subjective.