Most day traders have never run a business before they have always worked under someone else. Someone else has already developed a successful trading strategy and they are simply following that guidance. Most day traders do not want to admit that it takes a long time to master their skills. They think that they can start working in a few days or weeks by reading some books or watching some Youtube videos. Most day traders do not keep any trading records and cannot even remember what the entry price was. Most day traders do not pay much attention to risk management. They believe that losing trades will turn around so they do not want to close losing positions which leads to big losses.
Even if not closing losing trades don't make one lose excessive amounts, they are surely going to get their capital stuck if they haven't used stop-loss and are now waiting for the market to recover and get back to where it was when they bought.
This has happened with me, and many other traders as well as a newbie, because when you are inexperienced and don't understand much, you will have this kind of a mindset where you think that if you close the trade at a loss, you will lose money even if it's just a small percentage, so you should rather let the market go down and come back again so that then you can close the trade.
However, an experienced and knowledgeable person would think of it differently, they would think that if you have your capital free, and the market is going down, you can buy from a lower point, and then when the market reaches where the first trade was made, they will make more money than they have lost when the stop-loss was hit. I know that it might not happen all the time, because sometimes the market goes down, your stop-loss gets hit, and it goes up again immediately, but that is a rarity.