Trish, that's an interesting topic! I, too, get emails asking why I've chosen to make a particular heroine a virgin... and other emails asking why I don't make more of my heroines virgins.
Bottom line? For me, a heroine's sexual past may or may not be important to the story. That's pretty much what dictates whether I make her a virgin or not.
There are times I don't think the heroine's sexual background matters to the hero or the story, as in my current book, THE SICILIAN'S CHRISTMAS BRIDE. In this book, Dante's deep need for Tally and her deep need for him are what drive the characters and the plot.
Other times, it does matter. For example, you mentioned a heroine not having had the kind of deep, passionate experience with another man as she has with the hero. That's the case in the manuscript I just finished proofing, THE GREEK PRINCE'S CHOSEN WIFE. There, the difference between what the heroine felt sexually in the past and what she feels now, in the hero's arms, is telling.
In the book I'm currently writing, THE SPANISH PRINCE'S VIRGIN BRIDE, the heroine's virginity is integral to the story.
Maybe the bottom line is that each story we write is different, and so is each heroine.