Why So Many DIVs?

VWD 2008 Express.  Visual Basic.

Looking at the samplewebsite that comes with the ASP.NET Ajax Toolkit, I notice that the designer used lots of DIVs (DIVS within DIVs within DIVs).  This seems to be a fairly common practice, but one I have never adopted (I use tables and table cells instead).  Why so many DIVs and what advantage do I gain from using DIVs instead of tables?  Thanks for the help.
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