I guess its "just there" It adds very little value but I guess it doesn't hurt having a pit. If as a customer you want to send your order to the pit then go ahead and if not go to the screens. Its just one of those "why not?" situations. Its not like they take much room in the building.
I'm a trader down here in the hogs pit, but occasionally wonder over to the S&P if there is something going on. Still a lot of action in the pit and large institutional orders still go through here. Not only because of the order flow we can get, one of the reasons me and other locals still trade from the floor is the contract multiplier and tick size. It's 0.25 on the screen and 0.10 on the floor traded contract. We can go in a trade at 0.20 at 10 contracts and then get out a few seconds later at 0.40, which makes $500. And, then there is the whole thing with not having a real-time risk management software blocking trades if you go over margin. We're not monitored automatically like you all on the screen are.
It's also mutually beneficial for the pit to exist because it's an instant pulse check on the S&P. You can see and hear what's happening, much more transparent than the electronic system with algos, dark pools etc. Any institution can instantly see what's going on with the S&P by maintaining a presence in the pit.