In Alice's Adventures in Wonderland,why would Carroll frame the story as a dream that might not be a dream to present his overall message? Think about what adults do and say that seem to be “nonsense” to children even though adults often see what children do as “nonsense.”
There are several reasons why Carroll might frame his story this way. One is formal: it fits with many of the themes in the story, such as mistaking appearance for reality, words for physical reality, and so on. This is one more occasion of mirroring/doubling in the work.
Another major reason is psychological. Any apparent social critiques in the work can be dismissed as wisps of a dream. It is a way to say difficult or painful things and taking the sting away, like saying, "Just kidding!"