Swimming in Greenbelt

I went swimming yesterday after work. The local outdoor pool opened about three weeks ago and I have been trying to go two or three times a week. Splashing around in the water is one of the nicer ways to deal with 30 degree heat and 95% humidity. I can barely swim, so I tend to spend a lot of time sitting in the pool watching people, and I have come to the conclusion that thong swimwear for men should be banned. Greenbelt is not Rio de Janeiro, so why do some guys insist on dressing as if it was?