because no one will take the other side of your transaction......
do not forget you need a broker and he will know it, sooner than later and start taking the same side.
he will tell his good friends... who will then tell their good friends and soon everyone will be on the same side...the liquidity will dry up-because no one will take the opposite side-and then everyone has to exit......at the same time.......at a loss
According to your incredible stupid idea, there are no profitable traders at brokerages.

