There's a horrible stereotype of both the romance writer and the romance reader as somehow undereducated and unprofessional, when in fact there are a number of incredibly well-educated professional women who have chosen to leave their other careers and go into writing romance.
I went to grad school with the grand plan of getting my Ph.D. and writing weighty, Tudor-Stuart-set historical fiction - from which I emerged with a law degree and a series of light-hearted historical romances about flower-named spies during the Napoleonic wars.
One of our fundamental human needs is finding our partner that we hope we will stay with for the rest of our lives. You often find the same search in other genres. The mystery novel has a romance subplot. Literary novels often focus on that relationship but do not often end well.
I've had mainstream readers complain that the book is really a romance, and romance readers complain that the book isn't a romance - with the same book! It really depends on the individual reader's expectations going into the story, and that's very hard to predict person to person.
I've been typed as historical fiction, historical women's fiction, historical mystery, historical chick lit, historical romance - all for the same book.