Hi,
I think you asked some very profound questions. It's possible that society has created the idea of romantic relationships. Look at the movie industry/Harlequin Books/ even fairytales. Many times as women we dream about being swept away by someone who madly loves us.
As far as being told you're going to find someone and get married - I think particularly 40yrs ago alot of women just assumed when they finished school they would get married and have kids. Even today many single people think of themselves as incomplete because they can't find a partner. You're right when you don't have one, it makes you more compelled to find one and then you start questioning what's wrong.
I think it's better to just relax and concentrate on making yourself a complete person. Think about what you really want and the qualities you think are important in a partner. Relationships are hard, especially as the years go on. There has to be a strong foundation because when the passion fades a little - there has to be something to lean on. All the best