Well, I refuse to install Visual C .Net on my machine, simply because: 1) MSVC 6.0 still works for me 2) I hate to relearn everything from scratch as all the settings and much more have changed 3) I want to be able to create object files still loadable on older Windows versions, including LabVIEW real-time, without the need to copy SDK link libraries and runtime libraries from my old system into the .Net installation and fight with several more problems caused by this.
So I guess, a lot of the pros needing Visual C for LabVIEW development just don't use .Net yet ;-) You could also say CIN development is obsolete except for those people trying to get their older software to run and they probably don't use MSVC .Net. Instead you really should consider to create DLLs or shared libraries as they have nowadays almost only advantages including standard support out of the box from all the development environments you may have or wish to use.