Do you say the same thing about the Fifth Element? That's all it is. It's inspired by Leeloo, but with Jack's punk rock aesthetic.
And nipples poke through even in loose clothing a lot. It's only natural.
Kids don't care about characters like Jack, half of the time anyways. You're giving them too much credit. And if they do, they're cool kids. Like I was. 
Well yes I would, the purpose of Leeloo's outfit is also to show off her body.
And nipples do, yes - but it's a conscious design decision to do this. I can't really see what the purpose of it was except to titillate.
Don't get me wrong, when I was a teenager and early twenties I was well up for the sexy funtime characters. it's only as I have got older that i have realised how ridiculous it is.
Edit: and the other thing, of course, is that none of the men have visible nipples or carefully caressed nobs thrusting through their skin tight outfits - if they did then it wouldn't appear quite as deliberately aimed.