A few ideas: Autocompletion of the IDE: Netbeans or Dreamweaver, for example, but surely others too, tend to prefer - depending on the settings - these auto-closing tags over the unclosed Improved overview: if you see at one site, that there is a closing end, you know that you don't have to look for a closing tag Simple habit: Since the XHTML standard suggested this style of one-part-tags, many people had adopted it. And since it doesn't matter, why change?

What's to say about the upgradability to the next versions (6.4, 7, ...) - will it be easy or is a major refactor process necessary?