I think it's so that they can use css media queries. Here's a list of pros and cons for div background vs img tags: http://stackoverflow.com/questions/492809/wh

I think it's so that they can use css media queries. Here's a list of pros and cons for div background vs img tags: http://stackoverflow.com/questions/492809/when-to-use-img-vs-css-background-image http://stackoverflow.com/questions/492809/when-to-use-img-vs...