s nude body turns them on, because we generally associate nudity and sex. The
skin-to-
skin contact feels good, and intimate, which all contributes. Because touch/massage/licking/tickling with a feather/slurping honey off parts of the body other than just the genitals is a turn-on - that applies to men, but even more so to women.
So, nudity is not necessary, but it has its benefits.