I've never understood the idea of not using a SL, unless you're sat in front of your screen with your finger ready to click the close trade button. But then again how stressful, unhealthy and inefficient is this approach!
At the end of the day a SL, despite its name and perhaps incorrectly marketed meaning, is just a market order. If there is little or no liquidity at the SL level then it wont get filled at that level. It's just a back-up, but certainly not guaranteed at all.
Last year for example, when we saw the GBP/USD flash crash in October, +/- 1,100 pips in less than 60 seconds - a SL would have been useless.