I rarely update my profile so when I book a trip it always says one guest whether the trip is for business or leisure. But I do fill out the box for special requests. I'm sure no one reads it since I was never granted or acknowleged of my requests.
I just have to remember to change the number of guests when I book trips for my family. This might explain why I've only managed to receive 5-6 upgrades in 4 years.