Art works the same way; we remain unaware of layers of meaning when we lack the experience to understand them. As Goethe said, "We only see what we know."
Back when artists had less freedom to be explicit (and audiences were more sophisticated and patient) artists conveyed messages that went undetected by innocent viewers, but were understood by those viewers who had enough experience to recognize what was going on.
Here, some anonymous illustrator had great fun with an orange crate label:
Here, we see another suggestive fruit offering:
Similarly, you could probably fill an entire book with the facial expressions of beautiful damsels rendered thoughtful by the size of their hero's weapon.
Howard Chandler Christy
Robert Fawcett
What can I say? Most illustrators from that era were men, and this is apparently something guys like to contemplate.
Today we can scroll through images at breakneck speed without missing much because artists no longer need to communicate in layers-- they are pretty free to put anything they want on the surface (regardless of how young the audience is, or how ill prepared they might be for extreme content). Some artists believe that unrestrained art is better art. Others believe, in the words of Gorky, "When everything is easy we quickly become stupid."
Censorship and repression aren't the only reasons to resist spelling everything out on the surface; there are purely artistic reasons as well. You can only fit so much on the surface of a drawing. After that, if you need more room you have to start working below the surface. A layered approach to art can add depth and reward reflection. Most importantly, it adds the superior freedom that only ambiguity can provide.
I love this delicious drawing by Theodore Geisl of Terwilliger Frilliger spanking a cat while the other cats skittishly await their turn.
In 1929 (long before he became famous as Dr. Seuss) Geisl mused about the pleasure of cat spankery: "the peculiar sensation of indigenous largesse one feels when he spanks a kitten given to uncontrollable outbursts of hysterical guffaws."
Multiple themes co-exist in perfect harmony in this little drawing. On one level, the drawing could fit harmlessly in any children's book. But there are different flavors here for those with the palate to taste them.
Some of the best art is a layered experience. As with magnetic storms, you only become aware of the existence of additional layers after you've developed the capability to appreciate them.