Final answer:
Mr. Bennet ignored Elizabeth's advice about Lydia because he did not value her opinions and prioritized his own amusement.
Step-by-step explanation:
Mr. Bennet ignored Elizabeth's advice about Lydia because he did not value her opinions or intelligence, and he had a habit of dismissing her advice. Throughout the novel, Mr. Bennet is portrayed as a passive character who avoids conflict and does not take an active role in his daughters' lives. He often prioritizes his personal amusement over their well-being. For example, Mr. Bennet agrees to Lydia going to Brighton because he believes it will provide him with entertainment. Additionally, Mr. Bennet may have been influenced by his wife, Mrs. Bennet, who was eager to see Lydia married and did not place importance on Elizabeth's advice.