No reason at all.
The only reason I can think of is that you like mysterious errors, hangs, and other bugs and want to troubleshoot them. For DVD you NEVER use h.264, only MPEG2.
Hardware encoders like Matrox MAX are useful for speeding up H.264 encoding for the web or Blu-ray discs. But it sounds like you don't need it in your workflow.
Are you saying that if you use the Matrox, when you render your video, it will cut the time down quite a bit?
I don't know how it works on Windows but on the Mac it shows up as a QuickTime component. So any application that can export a QuickTime movie (QuickTime Player, Adobe Media Encoder, Compressor, etc) can export to this component and it will utilize the Matrox hardware.
Theoretically you could set your preview file format in Premiere to the Matrox component but I don't know how well it would work.