The idea of the Pickwick Club is the nucleus from which the novel grows. Once the action is under way the club is more or less discarded. In Chapter 1 we see the club in session. In Chapter 11 we are reminded of its existence, and then we forget about it until the end of the book, when Mr. Pickwick announces in a line or two that the club is dissolved.
The club is originally presented as a society for the gathering and dissemination of "scientific" knowledge. Mr. Pickwick undertakes his travels to collect curiosities and examine local customs. The club is an object of satire, of course, and Mr. Pickwick is a rather pompous old gentleman. To continue the club idea would mean perpetuating Mr. Pickwick as a caricature. Dickens clearly had other ideas for his development.
Mr. Pickwick's companions, Tupman, Snodgrass, and Winkle, are club members, but we forget this. In other words, the idea of the club is transformed into the idea of a group of friends under Mr. Pickwick's patronage. Their object becomes travel for its own sake, for fun and romance, rather than for information.
Thus Dickens turns a rather sterile concept into something flexible and rich with possibility.
Blotton, a club member who habitually tells the truth in a harsh way, is discarded in Chapter 11. But his function of telling the truth is taken over by the genial Sam Weller, who makes it possible for Mr. Pickwick to develop into a figure of high comedy rather than an object of farce.
In Chapter 39, with the episode of the scientific gentleman, Dickens measures the good Mr. Pickwick against his farcical beginnings in a rather pompous old man with pretentions to scientific knowledge. This device not only works, it is amusing.