I think people trade using market orders because option trading can be a complex system for the new traders.The spreads in the markets are dependent on the volume of trade plus the broker chosen. I have been trading in the forex market for several years. The brokers which I choose (Fxview and XTB for now) are for the same reasons. Ultra low spreads are essential for trading in a number of markets especially in forex. This is a very essential parameter to look for while trading. Option trading is also good and can give you higher win ratios as compared to market orders.