lol i had the same convo w my friend the other day
we both concluded that its bc swimwear is meant to be seen while underwear's undergarments? thats js what we have lol
different material, underwear can be slightly see through or not cover as much and is generally a bit thinner, but thats just the reason you dont wear underwear as swimsuits and vice versa
its mostly just different settings, as a man, you wouldnt just go outside in the city while shirtless, would you? but in the beach its expected, because youre getting in the water
its like how we wear different clothes to different places and circumstances, beaches, work, parties, weddings, funerals, hiking, school, home, theres different attires that would be considered "normal" in all of those
Yk what i had the Exact same train of thought when i was 10 lol
Whats the difference bw swim wear and underwear, they basically cover just as much ┐(￣ヘ￣)┌