Markets are always moving. I'm always adjusting positions. Most of my trading is option based. Vol levels are changing, spreads are moving, etc. My core position is a long term thesis. For example, I'm very long Oil. I have option spreads across many different months and strikes. I'm always adjusting them. Taking some off, adding some more, etc. Plus there is a lot to watch. Sure, you could look at charts at night. But you will miss a lot of the nuance. For example, you might miss that one particular spread acted differently this morning when X was happening. At the end of the day you will simply see the net result, oh this spread was down on the day. But you are missing a lot of information when in fact, yes, it was down, but it did not move at all when spread XYZ was blowing out. That's valuable information. Sure you "might" catch that from the chart. I know from my own experience I tend to miss these subtle clues when I just pull up some chart at the end of the day and look at the binary outcome.