I know you guys are all really knowledgeable about the game, but try for a moment think about those who don't. For everyone of us that knows a lot about the game, there's at least ten that doesn't know much. Talking way too deep might put off a lot of new viewers, and I'm pretty sure commercial-wise Sky would not want that to happen. "Left footed people on the right would cut inside" is basic knowledge for us, but I still know a lot of people that would go "Oh wow!" about that.
Furthermore, I personally finds Andy Gray entertaining, and I'm sure that's what commentators are for. If I wanna know something more about the game I would go onto the internet and analyze myself instead of wanting the pundits to tell me, but that's just me.