I can relate and not relate. I have 3 sisters and zillions of girl cousins I grew up with. I currently live in a sorority. When hanging around together casually and there are no boys around we frequently wear tank tops or tee shirts along with panties.
Boys seeing girls in their panties frequently give it a sexual or erotic overtone. It's most likely the reason girls avoid that circumstance in the presence of other males. At the beach, a bikini, which can look exactly like a panty, now has a social context that supposedly defuses the sexual overtone. Thus, girls are more likely to feel more comfortable in such environs.
