Difference between Lingerie and Bikni

It's the other way around. Women are more likely to feel exposed in lingerie, seeing as it's underwear, versus a bikini, which is intended for swimming (even if you never swim, and even if the garment itself is impractical for that).

Hell, I've worn slips which had way more coverage than swimsuits or shorts and a halter top, and I would rather be out in the shorts and halter top or a swimsuit.