In polite society of the Regency Period, only the eldest daughter and perhaps the second eldest (if they were close in age) would be expected to be present at public gatherings. When a young woman reached a marriageable age (determined by her father or guardian), she had a "coming out" party, at which she would be presented in women's fashions of the day, and would be allowed to enter the social arena of public and private parties and balls. The eldest daughter was always presented first, and after she was married, the next daughter could be introduced to society.
For the Bennets to have all their daughters "out" into society at the same time, with none of their other daughters married, would have been a great social faux pas.
