30 [M4F] help me understand underwear vs bathing suit

Is a little controversial and confusing whats the difference between female underwear and bathing suits and why are you comfortable showing off in a bathing suit showing off your body but if accidentally watched in your underwear or have a clothing mishap you're disgusted and traumatized when underwear is less revealing than a bikini. Lets discuss the differences, debate the facts, this weird fact about female clothing. Dms open.