I think [unknowingly], you ask a good question.
The Gemmorah at the end of Succah discusses exactly this topic. When Nisuch Hamayim was celebrated in the [second] Temple during the 7 days of Succot, originally [during the first Temple] the joy was so enormous, and everybody participated, including the Kings, that no separation was made during the celebrations even in the Ezrat Nashim in the Temple.
Sometime during the second Temple, the problem you mentioned emerged. Probably people got less spiritual, less obsessed with the Mitzvah of the Simchah and started gazing around. The Sages decided to stop the practice and install a balcony for women. This is how [probably] the whole idea of Ezrat Nashim started (there were no shuls yet).
The Orthodox movement (esp in Israel) took the idea a little further, completely separating men and women on all public occasions, all the Haredi shuls have a separate Ezrat Nashim, with a separate entrance with either one-way mirrors or thick fabric, prohibiting men from seeing women at all.
However less Orthodox movements took a less stringent approach. I also saw R' Moshe's Psak (don't remember the source) that concluded based on that Gemmorah that men are allowed TO SEE women during the service or celebrations with the Mechitzah being a physical separation only.
So back to your question. The described behavior happens either in less stringent communities that practice a Mechitzah in the first place, or is based on the premise that the men will exalt in their Midos beyond their primary urges, just like in the days of our ancestors.