The sexiness of an outfit is directly proportional to the perceived possibility that a vital piece of it might fall off.
This basic theory underwrites Stripperiffic clothing, Impossibly Cool Clothes, and pretty much anything else you stick characters into: what makes clothing sexy is the potential for a catastrophic Wardrobe Malfunction. The Trope Namer is William Ware Theiss, costume designer on Star Trek: The Original Series, who first codified the concept.
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Though Theiss was a costume designer, according to Inside Star Trek: The Real Story by Herb Solow and Robert Justman, most of the costumes — following this theory — were actually somewhat more modest before being “improved” by Gene Roddenberry.
What happened to sexy sci fi?
People realized they could just watch porn
Everyone is beautiful and no one is horny:
https://bloodknife.com/everyone-beautiful-no-one-horny/
No one is horny? Speak for yourselves, I’m horny all the time lol
I get it tho, movies don’t have characters with any libido.
And, everyone is beautiful? Speak for yourselves there too
The folks responsible for the sexy costumes, Roddenberry and Theiss, died in 1991 and 1992, respectively.
See also: https://tvtropes.org/pmwiki/pmwiki.php/Main/TheissTitillationTheory