I have tried trading with stop loss and without stop loss and there are some problems with a strategy without stop loss.
The first problem is that if the market goes up, you're still in profit but not as much as before. The second problem is that if the market goes down, you're still in profit but not as much as before. The third problem is that if there's no real news (like a war), then we can't get rid of our positions because they're already at their max size and won't go any higher (and the market will be flat). And finally, when the news comes out, it could be negative or positive and then your position could go up or down by a lot more than what you originally expected.