Because in some cases it can lead to a way bigger loss
than with a "mental" stop loss. Because by a fast crash
you sell unlimited to a very cheap price.
And after a big crash a stock comes often
back 20% to 30% percent very fast after you get stopped out.
I don`t use stop loss, escpecially on very volatile invests.
I watch the charts 1 or 2 times per day.
Works fine for me.
Big investors can crash a stock to
shake stop-loss-traders out.
But I´m a longterm investor.
I don`t care about 80%
up and downs in volatile markets.
One of the reason why traders loses their money after using this feature, especially inside volatile market, stop-loss is a good tool
but also can be a reason why you will lose your investments.
One mistake with your entry/exit positions will burned everything, you needed to check your position before placing your stop-loss position.
Remember that whales are just around the corner waiting for the big hit that will shake every weak holders inside the market.
Stop-loss is a continuous learning process, from time to time you will learned and adjust until you tuned the proper blend between
your traditional strategy and your stop-loss system.