nav234 wrote:
why it is considered to be de rigeur for XAML application development.
Because Microsoft thinks an arbitrary separation of programmers and "designers" would be a good way to make more money ($600 for the entire Expression library). Every question asked of Microsoft by a programmer regarding customization of templates elicits the same response from MS - "Using Blend, do this or do that....".
Problem - Expression Blend doesn't come with Visual Studio, so guess what? You have to spend as much for Blend as you did for VS... What a crock.