The use of stop loss may not be profitable to scalpers. Especially when the join a trade that is about to retrace unknown to them and it triggers their stoploss before moving in the main direction. Stop loss is best practice for day traders or position traders for scalpers they just have to monitor their trades and be disciplined enough to know the exact amount they are willing to lose from a trade and them take their profit and loss decision based on that.
When you're actively trading and monitoring the market, you don't need to have a stop loss in your trade. Stop loss are only needed when you'll not be actively monitoring the market. The stop loss helps you end a trade before it starts giving you losses. Stop loss can also put you in losses when it gets triggered before the market reverse and continue pumping. Stop loss should always be adjusted so your order don't end in losses.
Risk management when trading is very important, without it you'll lose all your money. The very first risk management I knew was not to invest more than you can lose into the market. Then always take profits while trading, don't be greedy or you'll regret making that decision.
I guess you have a little experience with trading which is the only reason why you can be saying stop loss is not needed in it. Perhaps you are trading only Bitcoin and other slowly moving markets that might be active without threatening your account, you can't dare to do this with other asset classes. Many that I know had done trading this way before and they all regretted it, but trading markets like Bitcoin and Ethereum have made people feel that it's safe to leave their trades floating freely without protection simply because they are less risky, but this shouldn't be a general advice to trading as a whole. What if a dangerous and sharp market movement occurred?
Mind you, it's not everyone that would have the time be sitting and watching the chart all day long, and the best way to calculate your risk management is to have your accurate stop loss, nothing else.