Modesty is quite important in Judaism. It's called tzniut
Even though the concept often refers to the way Jewish women are supposed to dress, it goes beyond that. Tzniut deals with many aspects of everyday Jewish life. For instance, you're not supposed to hug or kiss in public... even your spouse.
What's also not allowed? Staring at the members of the opposite sex. Not the worst rule, actually... less creepiness.
Other rules: no pornography. No looking at animals having sex. No immoral thoughts. (Ummm... that one is pretty tough to enforce.)
But it still boils down to how to dress, both for men and women. The key point: cover up as much of your body as possible.
Which brings us to Iggy Pop, who has preformed shirtless on stage into his 70s.
Why would anyone ever think he is a Jew!?