The word "immaturity" can, in certain contexts, conjure up a picture of childlike innocence. Toilet humor, for instance, is "immature", but it brings back memories of youthful innocence and the time when bodily functions were still novel. It can make you laugh because it's juvenile and nostalgic.
There is another kind of immaturity that is not at all pleasant. It is that of people who have not learned how to handle life. This is the teenage, pubescent kind.
These are people who in their thirties and forties still have tantrums, still have issues dealing reasonably with others, and controlling their emotions.
Immature people are a burden to themselves and to the people who get involved in relationships with them. Never learning how to escape your adolescence and get into adulthood is a kind of retardation, a kind of defect.
If you are one of these people, you probably won’t know what I am talking about. You probably would not read this far down the page either.