UML is only of value if the people designing the system cannot write the code themselves. ie, UML is a 'language' that communicates the architectural concepts to someone else, now if you're the person who is designing the code and implementing it, then why would you need to show yourself what it is you're going to do?! Get on and head straight for the coding instead. You'll still have to document what you did later, but the overall efficiency is quicker.
But, if you were a system architect wanting to tell your outsourced team of developers what you wanted, then you'd have to tell them somehow, and that's where UML comes in. However, I think that there are plenty of alternative means of performing this task nowadays, and frankly, the complexity of the UML diagramming means everyone has to understand how to read it, which is somewhat self-defeating if they don't.