Many retail traders forget to or ignore SL and it ends by costing them there precious money because of liquidation. The market can be very unpredictable and volatile all of a sudden and before we realize our money is gone. SL prevents that from happenning. Big market whales use SMC to target liquidation from small retail traders. So it's alwats mandayory to use a SL. Even if you would still be at a slight loss after your trade hit Stop Loss it manages your risk and you could always make more profit from your next trade.
Remember,
No one is giving your liquidated money back. So manage risks and use SL always traders.