Forex Trading - Why Stop Loss?

In trading, stop loss play a very important rules. This should be the first thing you need to focus on first before the profit. I am not sure about you, but among all the trader I meet that trade without placing any stop loss, often stuck holding on to the losing position. They are hoping for the market to come back some day.... "Some day"? Some of them stuck for more than 2-3 weeks or few hundreds pips. The worst thing is when you are holding on to a losing position for too long, it will effected your emotion on other new trade. Then you will never trade right.
Some times when I think of it, it does not make sense. Most of the traders that stuck with losing position that holding on for weeks are mostly intraday trader.
Knowing how to place your stop loss means how to secure yourself. Just as you are in a boxing match. Which do you think is more important in a boxing match, avoiding from being hit or to the punch? If you cannot protect yourself from being hit in a match, you will get knock down in round one. Is the same in trading, if you do not know how to protect your trade then you get knock down with big loss in the beginning of the day.
Let go your "Hope" method, it does not help you at all. Hoping is gambling and it does not fit in the trading floor.