I ask myself why and the answer could be double.

The first answer is that the programmers are lazy and they don’t want to learn the use of new tools that are not always so easy to install and learn.

The second answer is that a lot of tools are not well integrated in the IDE and take time to get confident with their usage.

I think that for a massive use of these practices (Test Driven Development, Continuous Integration, the use of a Source Control System) the various supplier of these tools must do a little step to that lazy developers to give them the needed integration that a Microsoft developer wants. One alternative solution is to wait that Microsoft release some tools that are usable for these practices (and not too expensive!) and for what I see Visual Studio 2010 is on the right way.