"its not their fault she dresses that way..."
True enough. It is a sad situation when a rich (and pregnant) star has nothing to wear but too-small undershirts, running shorts and flip-flops. Maybe she feels that if she puts some decent clothes on it will be granting a victory to the photogs.
No telling. Maybe she thinks she looks good. I don't suppose I look any more elegant in Wal-mart sweatpants and t-shirts from my son's track competitions ... but at least I'm covered :-).