I think it does help channel the airflow. The key is making sure you do your sanding near where your dust collection is. I know that sounds obvious, but placement really is the key - and you don't always sand in the same place (think of bowl near headstock and spindle across the bed).
The dust hood is actually left over from a HF set of hoods and hoses I purchased when I first got a dust collector. It is technically called a table saw dust hood. I have seen where some people have constructed pretty elaborate setups, and even used a bowl with a hole in the bottom.
Remember, it really there for dust, not flying chips.