Let’s be clear that those “good reasons” are vague, and the lines that have been drawn are arbitrary. The ages for all those activities vary widely from one country to the next (even state to state within the U.S., for sexual consent), and there’s no evidence that ours are any more reasonable or produce better results than any others.
(In fact, they may produce worse results: compare alcohol-related problems in the U.S. with those in countries with lower drinking ages. The United States has a higher rate of alcohol involvement in fatal auto crashes than other countries including Australia, France, Germany, and the UK, where drinking ages are lower. Cite: U.S. Dept. of Transportation)
Your logic is circular - the existence of statutory rape laws doesn’t prove that minors are incapable of dealing with sex, any more than voting laws from the 1900s proved that women were incapable of choosing leaders. Unless there’s evidence to the contrary, we should presume that people can make their own decisions, regardless of age.