Kelly Clarkson concert kimmel hollywood samsung at&t summer krush

The American Idol winner performed at the Samsung/AT&T Summer Krush event on Jimmy Kimmel Live yesterday and, how can I put this delicately...

Why does Kelly Clarkson wear such tight, body-hugging clothes? I don't get it! So she's not the thinnest pop star - so what? We can't all be Lindsay Lohan. But then don't wear clothes that don't fit!