Like brianorca said, baskets don't contain the flour that comes out, or whatever is on the surface of the bag. Plus some baskets have enough in the way of hard edges to damage flour bags, I've had it happen in the store while carrying stuff to checkout before. Only three times ever, but still

Kinda depends on what the basket is made of and the design, I guess. Like, an old school woven basket could work fine as long as it's well woven, but the typical shopping basket in stores is going to suck.