There are many mythical creature out there: vampires, wood nymphs, unicorns and people who work in layout tabs with modelspace active.
I've met exactly two people who do this, and both were civil drafters with a long history of AutoCAD knowlege. At first I was dismissive of this concept, but the more I think about it, the more I can see where it might be handy.
I decided to try it for a few days. It was uncomfortable, yet exhilerating; much like wearing your underpants backwards.
- You can work in a DVIEW > TWist mode without messing with your modelspace.
- You don't have to worry about what layers you freeze and thaw, as you are not affecting the main model space. However, the better way to work is to use the layer states manager.
- Civil 3D pops you back into the model tab after some operations. For instance, after I imported points, I was shot back to "real" modelspace. It feels like Civil 3D was not designed to work this way.
- VP scale is constantly changing as you zoom around. When the drawing is regen'd your text updates and can be a mess to work with.
- Seems to slow things down. It took a few beats longer to, say draw an alignment.
So, if you've ever wondered what this button does and if you should be pushing it - just say no.