"After-hours trading" and alternate venues allow one to trade outside of regular market hours. However there are a few reasons why you would not way to:

• The purpose of an exchange is to improve liquidity by gathering all buyers and sellers in the same place at the same time. If trading was 24/7, not all market participants would be trading at the same time.

• Some markets (including NASDAQ) depend on market makers or specialists to help liquidity. These exchanges are able to mandate that the market maker actively make a market in a security during a meaningful percentage of the trading day. Requiring 24/7 active market making may not be reasonable.

• Trading systems, meaning both exchange infrastructure and market participant infrastructure, need maintenance time. It's nice to have the evenings and weekends for scheduled work.

• Post-trade clearing and settlement procedures are still somewhat manual at times. You need staff around to handle these processes.

Hope this is helpful

"After-hours trading" and alternate venues allow one to trade outside of regular market hours. However there are a few reasons why you would not want to:

• The purpose of an exchange is to improve liquidity by gathering all buyers and sellers in the same place at the same time. If trading was 24/7, not all market participants would be trading at the same time.

• Some markets (including NASDAQ) depend on market makers or specialists to help liquidity. These exchanges are able to mandate that the market maker actively make a market in a security during a meaningful percentage of the trading day. Requiring 24/7 active market making may not be reasonable.

• Trading systems, meaning both exchange infrastructure and market participant infrastructure, need maintenance time. It's nice to have the evenings and weekends for scheduled work.

• Post-trade clearing and settlement procedures are still somewhat manual at times. You need staff around to handle these processes.