The social structures of the period limited the ways in which people could behave without being ostracized from their social circle. For example, only certain forms of employment were acceptable for "gentlemen" -- being an officer in the military, clergy, and, to a limited degree, law and medicine. Often men with no interest in or talent for those occupations fell into them due to social restrictions. Women of the gentry were expected to marry gentlemen -- to marry inappropriately or to earn one's own living was to remove oneself from the social category of gentlewoman (governesses, ill-paid and ill-treated, were sometimes an exception). Much of the lack of freedom in social choices is seen in the novel in the treatment of good and bad marriages -- whether Darcy marrying down, Lydia almost ruining the family by impropriety, the shame of having relatives "in trade", etc.