CSS: Why use span over div if displaying as block anyway?

Ive noticed a few sites (forget which ones exactly) that use spans for design elements (no content) but set their display to ‘block’ in CSS. Is there any reason that divs arent used instead? They are afterall inherently block elements.

The only thing I could think of was that these spans were part of the design of the parent block element and specifying them as being spans help identify them as being part of that block and not new block containers within it. Sound right to anyone else? Or is there some other underlying reason Im missing? :afro: