True, you should wait until you're 15 to try coke.
On a more serious note, that's quite a biased way of thinking about cocaine use. The plant/substance doesn't have the same stigma in, say, Peru, where a 13-year-old is quite likely to have chewed coca leaves or drunk coca tea on many occasions. The perception you have of cocaine use is very much a product of the community in which you were raised.
Obviously it was hyperbole, but OP was sloppy when they stated "it is perfectly normal for people to experiment with substances when they come of-age.". What are young people (13 year olds? 18 year olds? 20 year olds?) and what drugs (just weed? any drugs?)? Others chimed it and argued that kids naturally alter their consciousness by spinning around and nobody thought to clarify.
I don't think it's natural for kids to smoke marijuana. It is something that SOME kids do, but it is not natural or inevitable, and it is categorically not good for them (from a brain development, mental health, time-waste and addiction standpoint). There is a tendency for people to minimize marijuana risks and get sloppy around pot usage by kids.
Chronic drug use is no joke, but at least half the people I know used psychedelics in their early 20's.
Most people drink, and most people have used cannabis at least once.
What isn't normal is demonizing all forms of substance use, without properly differentiating it from substance abuse.