Because if she wore that stuff, she deserved it? Are you posting from Pakistan?
No, Brazil, where 66% of all citizens, including women, said in a recent poll that if a women dresses like a slut she is partly responsible for being raped, if it happens.
Now, that wasn't my point but I was surprised by the candor of even the ladies of Brazil. But a 20-something gal like Madonna making a gazillion dollars by putting out the industry's first racy CD ("Like a Virgin") and doing drugs with cool and fast guys each night, is no doubt likely to find that one of them has violent tendencies and, after an hour of snorting coke with her in her apartment or at a party, decides to take liberties.
I won't believe for a minute that Madonna was innocently knitting and reading her Bible, with a glass of warm milk at her side, when the dude pulled out the knife and forced her to the roof. Context, my friend, context.