>>57013404I think its mostly due to the Anime and how they were portrayed in game.
And their designs of course, being its hawaii, and that usually means beach, which means swimsuits and open clothes. All of them show at least a bit of skin, some more than others.
Lillie is obviously a main character + see through dress + later mini skirt + blonde + innocense
Mallow a tan tomboy + cook + green hair + booty shorts + energetic
And Lana for me personally is sassy but sweet tomboy + blue hair + one piece swimsuit + feet + flip-flops + smug + petite.