In my opinion, bikinis look like underwear. If I wouldn’t walk around in public wearing only a bra and panties, I don’t think a bikini is appropriate, either.
In my mind, bikinis aren’t very practical for swimming in, anyway. Every swimsuit I have seen on a woman who swims for sport has been a one-piece suit.
So, if a bikini is generally not “practical” swimwear, and it looks like under clothing, what purpose does it serve? Most of the girls/women I know who wear bikinis are doing so because they want to draw attention to their great figures by wearing minimal clothing at a pool or beach.
I used to wear bikinis, with a swim skirt, because I have such a short torso that I couldn’t find one piece suits that fit me. I am very happy I can buy a tankini now, instead of a bikini.