A big plus to many people on the high quality skimmers are that they consistently operate at a high efficiency. I would imagine most would want to mimic that as much as possible. Using a venturi would definitely improve reliability and efficiency, as well as cut down on maintenance.
Additionally, having tried this, I found that the amount of air it puts out can easily exceed the correct ratio based on the flow, therefor airbinding the pump is put prior to the pump. Placement before the pump is best as the impeller will aid in splitting the bubbles into smaller bubbles, allowing for more contact surfact with the water/air.