I picked up a little book of literary criticism on S&S from Penguin Critical Studies by Isobel Armstrong.

She has some quite strong words to say about Sir John, calling him an 'eternal child' and writing of his 'compulsive and coercive pursuit of group enjoyments', his 'addictive need to organize parties ' and the 'compulsory social enjoyment' he inflicts on everyone. She says this is a sign of immaturity.

I've never really thought of Sir John as being immature before, but I have wondered about the continual socializing. However, the gatherings he arranges typically have so much noise that people can't have a proper conversation. It seems like he just wants to gather people together to have as much noise and commotion as possible, and then call that fun.

I thought that it might be to compensate for something lacking in his marriage--if there are lots of other people around, then he doesn't have to be alone with his insipid wife. Or that maybe he acts immaturely because Lady Middleton treats him like a child?

But he is equally anxious not to have her be alone either. "Sir John called at the cottage one morning, to beg in the name of charity, that they would all dine with Lady Middleton that day, as he was obliged to attend the club at Exeter, and she would otherwise be quite alone, except her mother and the two Miss Steeles."