In the 19th century, elopement was completely frowned upon by society. It was seen as something that would shame the family and bring down the family name. Society would not have agreed to the marriage due to the parents feeling that the marriage would not have been successful because of the difference of status. Lydia's parents are expected to pay for hers and Wickham's wedding. Money, business and status was the main reason marriages were to happen and if neither parents or society approved of your decision, elopement was your answer.
Lydia and Mr Wickham decided to elope without anyone knowing because they knew that their parents would not approve. However, I feel that they concentrated less on the part where they have to face everybody again and how the family would never be able to get rid of this bad reputation that has now been formed because of them, especially towards the rest of the Bennet girls. To elope in the 19th century, you must travel to Scotland where you wouldn't need anyone's consent. In order to travel to Scotland, the transport was either by horse or horse and carriage (which travelled at around 5-7 mph), the process took many weeks. Society would have thought that Lydia was definitely impure and touched before the time she had reached Scotland where the marriage was to be secured and completed. This would have definitely affected the rest of the Bennet sisters in terms of attracting future spouses. Society believed that if one Bennet sister can elope, what is stopping the rest of them? They were all brought up by the same people.
Premarital sex was viewed as one of the biggest sins you could commit in19th Century England. It was seen to be pure and loyal to save your virginity until your wedding night and if you were to lose it before then you were seen as a slut and no longer respectable, this furthermore would have entirely