Good default, I’m of the same opinion, in general. We should only restrict entry age if simple education isn’t enough - as can be seen by teen suicide rates rising in parallel with the spread of social media.
Sugar isn’t restricted but alcohol and tobacco are. Why is that? Because there’s a difference in addictiveness and possible harm done.
I don’t know about addictiveness but sugar isn’t as harmful as alcohol, for example. Don’t get me wrong - in my opinion the negative effects of sugar aren’t taken seriously enough but they are far less pronounced and further down the road, while you can easily destroy your whole life in a year of alcoholism.