For me personally with the real life workload, for most of the case I don't have time to do day trading where you constantly need to check the chart of your assets regularly to make sure everything is under control. With that hassle, doing long-term trading and in my case DCA is the best and comfortable strategy for me because it requires little to no effort to check and you can forget it for few years and grab more if necessary.
Yeah right, if you don'thave time to keep engaging yourself and monitoring how the market behaves then better to use that long term investment style, just buy and set your target and leave the market, you only need to monitor once the market is on its way pumping just to check if you already reached your target and collect the earnings that you think is managable to earn.
Not everyone can devote much or all of their time to the market. But whether we choose trading or long-term is not just because we don't have time, we need to choose which method is suitable and gives us the best results. If you could make more profit from trading than from your main outside job, I bet you would quit your job immediately and dive into full-time trading.
Trading is not easy and even if you have the time and knowledge there is no guarantee that you will definitely make a profit from it. Making profits from trading is extremely difficult, which is why most people prefer to invest for the long term.