You're missing the point. If there are predators walking around, why would you carry a steak on you? That is why in basically all the madhahib, the level of fitna directly correlates with how covered a woman should be or if she should be allowed to leave the house at all. The primary blame of course lies with those who would rape and attack women, but if a woman knows that if her showing her face or wearing jeans will attract unwanted attention, should she not be more covered? In the Shafi'i madhhab, according to some scholars, it becomes obligatory on beautiful women to wear niqab because they're beautiful. Is it their "fault" that they're beautiful? Of course not. But if a woman is beautiful, she will attract unwanted attention, from both those people who aren't obsessed with sex and those who are, even if she is wearing what would be considered proper hijab but the rules change when there is fitnah around and that "proper" hijab would not be proper because of the fitnah. And are you seriously trying to compare loose garments with jeans? Jeans are really form fitting. Some ulama even say that men shouldn't wear jeans and tight pants without wearing a long shirt over it so what makes you think it is in any way permissible for women to wear them in public?