Good Question, and one I was quietly pondering myself a few days ago at the beach.

The only theory I could come up with is this. Blame fashion trends. The thong as underwear came about originally so women could wear shear, close fitting, light coloured pants, and not have a VPL. The whole idea was to hide the garment, not expose it. Obviously this worked, and popularity grew, the other benifits becoming obvious later (comfort, sexiness etc). Then look at the flow-on effect in swimwear. Women not wanting their g or thong to be seen, as undies weren't meant to be. That and the fact society seems to have become a little more conservative in some ways. Just a theory. And don't ask me why thongs started jumping out over the back of jeans, and not onto the beaches. Swimwear has gotten smaller from the top down lately, not skimpier from the bottom up!

I have also seen it mentioned that younger people will do the opposite as the generation before them as a whole, hence the general decline of thong wearing even in places like Brazil. The whole fashion-generation thing goes around and around, so it will probably swing back the other way in another ten years or so. I'll just continue to wear thongs. They ain't gonna dissappear altogether.

I agree.  And the same goes for thong leotards as well.  When thong bikinis and thong leotards were really popular, thong panties hadn't taken off yet.  Once thong panties took off, there was a decline in bikinis and leotards.  I tink it has to do with the fact that when thongs panties first came out, they were considered sexy.  As they became popular, they were considered more functional rather than sexy.  I mean, just about every woman owns at least one thong (I embarrassed to say that I know even my mom owns at least one pair, and she is 60 years old!).  And when women go to the beach, they want to look sexy, or to be wearing something with an "edge".  The thong just isn't as "edgy" any more.  And many fewer women call pull off the low riding short shorts type bikini and really look good, so it is more impressive for them if they do.    The thong, although more revealing, was better suited for more body types.  More women could pull it off.

I'm hoping, with a lot of return to 80's fashion right now, that the thong leotard makes a comeback.  To me, it is the perfect combination of sexy and comfortable.  Most of the women I know my age would welcome its comeback.  And again, it suits more body types than the short shorts mid riff bearing workout wear.

Thanks for your comments!

I guess availability could be an explanation too. I don't know about womens thong swimwear, but I guess they are not so easy to find in shops nowadays (due to the fashion trends). Mens underwear thongs are not common, but still available in shops. While mens thong swimwear are impossible to find in ordinary shops. You have to go to the internet or maybe specialized shops when buying mens thong swimwear. At least this is my experience. I guess it's about the same for womens swimwear.