[vineyardmike]

Because once upon a time people had to go in person to a building to trade and no one wanted to do that 24/7.

Now, we still maintain that for some markets. I'm guessing its a combination of laws, inertia, and the ability to do outside of RTH news/sys updates.

Some markets are open much more than the 9-430 stock market - for example futures markets open sunday night.