The genre of romance is one of the most successful genres of literature. Many authors try their hand at writing romantic literature because they realize the market is so big. People do very well with their books and some even become millionaires because the market is so massive. Romance novels are high on the sales list because Readers have certain expectations for each novel and they're thrilled when these expectations are met because of an emotional payoff.
Back in high school, you may have learned that the traditional story includes an introduction, the rise with a bit of drama, a final climax where everything comes to a head, and then finally the conclusion where things are worked out – ideally with a happy ending. It's the same kind of set up that romance readers expect from their authors. It may become rather repetitive for authors to write the same kinds of stories where their main hero always get the female character. In the end, readers want to feel that happy ending.
Emotional connections are important
As a romance author, it is your job to give readers what they're looking for.
They want an emotional connection with the characters in your novel and many of the readers want to see the woman get the man of her dreams in the end. If the female character does not get the man she wants, many people wouldn't classify it as a romance novel. There is a sense that each book has to end with someone floating on a pink cloud and possibly planning a wedding.
Think about this: if you kill off your hero at the end of your story it's still possible that that story will have some elements of love. Sure, you may have written a perfect Love Story but the fact that one of the characters dies, in the end, will classify this book as a romance. This is because you have removed the emotional payoff that readers expect, which requires that both the male and a female – or whoever you're focusing on – are alive and together in the end.
But that doesn't mean they can't be sacrificed.
Remember the dark moments
Like any new relationship, two people have to figure out how to make it work. In real life, nothing is perfect and life surely isn't a bouquet of roses over time. Any love story will have a set of thorns or dark moments and you have to make sure that you highlight these in your novel. If two people fall in love and they have a happy ending, the story might not be interesting to readers. Instead, they want to see sacrifices, hardships, and possibly even experience a moment where the two might not find each other. But it's your job to make sure that love is found and that everyone is happy as your novel comes to an end. That's the requirements for romance: romance requires mutual satisfaction for both the characters and your readers.
Are you surprised that romances always have a happy ending?