Why impose limitations for the sake of imposing limitations? If some people want to trade on the weekend, they should be able to trade on the weekend. No one is forcing you to trade on the weekend.
Well the idea is so that the market is not so volatile due to outside forces. Also people wont FREAK OUT cause they ordered to withdraw their money on Sat and its Monday morning and "WTF ITS NOT HERE!" In my opinion less volatility I think is better for the market.
That's the beauty of the free market - it corrects things like this automatically, without regulation. Have you noticed that there is less and less of a dip on the weekends, since more and more people have recognized the dip and decided to take advantage of it? Their taking advantage of it means that they are selling during the week when the prices are theoretically higher, then buying on the weekend, when the prices are theoretically lower. This causes the price during the week to drop, and the price during the weekend to raise, evening out the discrepancy.
Not only that, but there would be no way to force ALL exchanges to cease activity on the weekend. The moment one exchange closes for the weekend, people will simply move to the next exchange that doesn't close on the weekend.
