I doubt "The Notebook" had as much bearing on love and relationships as simply having more "options" and higher expectations. This is especially true for women. Today's women expect more out of life, love, and marriage than previous generations.
In past eras like the 1920s, 30s, 40s, 50s and even early 60s a lot of women either had no job or had a low paying job without much potential for advancement. The goal for a lot of young women was marriage to a reliable man and having children. Oftentimes when women left their parent's house it was to move into their marital house. It wasn't uncommon for many couples to get married soon after high school graduation.
Some women whose parents had money went onto college with the mindset of meeting an ambitious young man or one from a "well to do" family. Education was a secondary objective. Most women were married by their mid 20s and those who weren't were often pitied.
Marriage was "for keeps" even if one had "buyer's remorse". People often would say; "I made my bed and now I must lie in it." Divorce presented a hardship on women in particular who had no job skills or little education. They were for the most part dependent on their husbands financially. Divorce also had a (stigma) attached to it. These things caused many women to stay in marriages that were unhappy and unfulfilling for them.
According to a recent survey from AARP today women initiate the filing of 66% or 2/3rds of all divorces in the U.S. Better career opportunities and higher pay gave women more financial independence along with better birth control methods which made it possible to have sex without fear of pregnancy were all contributing factors in changes within the dynamics of relationships.
The more options one has the less crap they're going to put up with! LOL!
Personal computers and online dating has created a "shoppers mentality" when it comes mate selection. We can now scroll through various profiles and photos from around the world. There is always the feeling that one can "do better" if they're willing to (keep looking or hold out). No one wants to "settle". We believe if the person we're with does not make us happy there is someone else out there who (will) meet all of our expectations!