You may not believe this, but many European pools only permit speedo-type suits for men. Seriously. I found this out when I was researching our trip to Paris. If you search on the DLP board, I bet you will find queries as to whether the Disney hotels require speedo type suits.
I have NO idea of the rationale! Imagine being an older heavy male and being REQUIRED to wear one of those if you wanted to swim. I can't imagine what I'd do if our city pool told me I HAD to wear a bikini!