Why were friendships so important?

The specific frienships addressed in the novel serve to move the plot. Each of these friendships runs interference in one way or another, and although, the interference is for the most part well meaning.... it doesn't always seem so. Darcy tries to protect Bingley from what he considers a bad marriage. Elizabeth regularly runs interference because she believes the match between Jane and Bingley to be a good one. Elizabeth's friendship with Charlotte is similar and because of that friendship.... Charlotte discovers Mr. Collins and a marriage of her own.