gavra, I totally agree with your assesment. But my theory regarding having no yiras shomayim in certain areas is because there seems to be blockages that people have towards their sin of choice that escapes their fear of heaven which they do have otherwise. I have seen women/girls daven with great concentration, having that personal connection to the Aibishter, while their knees are uncovered.
These women/girls are yirah shomayim. They will fear other sin like loshen hora, but because of peer pressure or other reasons, they do not have a fear of Hashem when it comes to tznius.
We all as humans have failures, we struggle with our yetzer hora, but usually if we fear Hashem we can say next time we won’t get in kaas, next time we won’t speak loshen hora, but there is an awareness of sin.
Lgabeh tznius, which is not a character habit that one chaps afterward, rather conscious desicions which cloths to buy, some people who do have yiras shomayim simply will not think about whether they are doing wrong tznius-wise even though it’s pretty obvious, for example they wear very tight-fitted clothes.