For people in satisfying and committed relationships—or at least pretending to be—there’s Valentine’s Day, a holiday in which romance comes connotations with love because, at the time, red dye was expensive and seen as a luxury. That a red rose provided similar visual appeal made it seem special.
Practically speaking, the idea has endured because unlike other flowers, red roses tolerate transportation pretty well. They’re a good blend of aesthetics and hardiness, two good traits for flowers that need to be portable as well as striking.
Roses are, of course, expensive, and if you’re more into the sentiment than the cash layout, you can find other ideas that can express your affection without contributing to the floral industry.