Why is it...
...that "Adult Content" always denotes anything sexually explicit or erotic?
How come it doesn't mean something intellectually stimulating?
Or anything explaining the complexities of life?
Or a refined insightful, reflective, and philosophical perspective of serious or significant subject matters?
Or a deep intimate understanding of the ways of life, the world, or the universe?

And just because a subject matter is of a sexual nature doesn't necessarily mean it is being handled in a refined and disciplined manner.