Why do the Bennets allow Lydia to go to Brighton?

In Chapter Nineteen, Lydia receives an invitation from Mrs. Forster, the wife of the regiment's Colonel, to accompany her to Brighton. Elizabeth entreats her father to prevent Lydia from going, explaining that such an experience will only increase her frivolousness. Mr. Bennet does not listen, insisting that Colonel Forster will look after Lydia, and anyway she is too poor for the officers to seduce.

In this scene, the parental negligence of the Bennets becomes increasingly more clear when they allow Lydia to go to Brighton. Mrs. Bennet supports the trip and wishes should could join. Mr. Bennet simply does not care. Mr. Bennet's negligence is perhaps worse than Mrs. Bennet's, since he recognizes Lydia's faults but is unwilling to do anything to change her.