One of the biggest misconceptions about romance novels is that they have sex in them. A romance novel can range from sweet, in which all action takes place off the page, to spicy, in which the author goes into graphic details about the act.
The main goal of a romance novel is to show a couple overcoming internal and external conflicts in order to achieve a happily-ever-after or a happy-for-now. Sometimes they may have sex during their journey; other times they may not believe the act is necessary for them to achieve their goals.
Whether the characters consummate their relationship before the end of the story depends on their beliefs, their goals and the situations they find themselves in. Therefore, before an author adds a sex scene, she should ask whether the act will help move the story forward or if it is simply filler.