Notice the difference in the behavior of these two radio buttons? Try clicking on the text that accompanies the first radio button, and then try the second one. When you use a Windows application or a Mac application, the text associated with a checkbox or radio button can be clicked on to select the given control.
With web apps, it’s necessary to use the label tag in order to achieve behavior identical to the Mac or Windows. This tag has been around since HTML 4.0, which has been around for about a bajillion years, by Web standards. The point is that no one has an excuse for not properly supporting the label tag correctly.