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You said really well that a professional trader always use stop loss .Its a great option to decrease your losses and give you a high ratio profit always .I think your friend may be don't have much knowledge behind that .He will surely learn it when he will make a huge amount of losses may be he can lost his everything .Its very good to know that you have this idea and you can apply it .
We are not going to argue if someone does this strategy or not, it was their choice and who knows if they are also comfortable without this thing. This stop-loss strategy is just an option to save from losing a huge amount but if we analyze it thoroughly, we are still at loss. That is why some people don't make themselves at ease with this but they choose to have their own of way winning against losses.
Everyone is at liberty of choice in stop Loss usage. People who have a large stop Loss limit most likely will not want to always use it especially if their stop Loss is hit and trade goes their way. It's always painful. They will rather leave the trade and watch it closely.