Here's what happens in In The Night Kitchen. A little kid falls asleep and floats up to a magical giant kitchen where he falls into a bowl and GETS BAKED INTO A CAKE! He somehow survives, flies a plane made out of batter, gets stripped naked and chased around by three identical Oliver Hardys wearing chef's clothes. It sounds more like a fever dream than a kid's book. That's some HP Lovecraft type stuff right there.
Yeah, boredom sucks. But if you just try hard enough (and own a pair of kickass wolf pajamas), you can turn your bedroom into a forest and become the king of monsters. And if you tell me that you never wanted to be the king of monsters, then you, sir, are a liar.
Also, sub-lesson: Threatening to eat someone up is not polite, no matter how much you love them.
Fact: everyone needs to be able to count. But in Sendak's world, it's not to count boring stuff like money or marbles or fingers. You need to count to be able to keep track of the crazy shit that keeps bursting into your house. How else will you know when the tiger selling clothes shows up? Also, what kind of crappy robber just takes a shoe? That turtle's probably worth way more on the black market, man.
The most important lesson Sendak ever gave: if weird hooded homunculi come to take your little sister away, maybe put down the french horn for a minute and deal with it. Goblin-based baby thefts are a growing problem in this country.
Because otherwise you might get eaten by a lion.