Passion, intensity, interaction. Things that make it more of a full-body experience rather than just involving one or two areas. It's fine to be focused on them but there's a difference between intercourse with someone with minimal interaction, and the same act - even in the exact same position - that includes touching, kissing, biting, grabbing other areas as well. For example I love it when a guy's got his hands in my hair at some point during sex. Not just hair pulling but fingers in my hair, hand on my head, and he's kissing or biting my neck or looking me in the eyes while fucking. It's a small thing but it just brings it up to a different level.