Because then you get to spend a day feeling like you live in a HAZMAT scrub-down zone. Hooray!
What's really going on here is the sanding and spray-texture that finishes up the sheet rock work. Instead of having a gaping hole in between the two rooms, now we have one seamless surface. The last step is the gigantic trench in the carpet. I'm working on a temporary drawbridge to span the gap, but hopefully soon we'll be getting new floors and that will solve the problem. Keep your fingers crossed!