There are a lot of reasons for leaving mid day.

Number one for me is social. We hunt alone, ambush hunting, at lunch we see how the others did. We BS, get warm, plan the afternoon hunt. Having lunch in town helps the restaurant to remain profitable. Without hunters, I suspect that some of these businesses would fold (motels and gas stations included). If they fold, the quality of life is diminished for all of the residents of the town. We do a small drive after lunch if conditions warrant. One year cousin left a strip of corn about 40 yards wide and 1/2 mile long. We had not way of knowing that this strip would be there ahead of time as they were actively combining the crop (not that field right then). We did the drive, got two deer, and then hunted separately until dark. Meeting at midday got us those two deer.

Two, it gets old, sitting all day.

Three, it is often too cold or too wet to sit all day without a break.

Lastly, it is supposed to be fun. I don't understand why so many people turn hunting, and fishing too, into competitions. (or endurance tests) People keep score to such a degree that they are appalled if you actually eat a bass or a trout. The different "bass" organizations have ruined bass fishing as far as I'm concerned. We will have two hunters with us this year who have never shot a deer. Anything they shoot will be alright by me. I am going to ask that the others shoot does and let small buck pass. Big buck are fun and they won't get that way unless they survive being little.

Bob

I decide where I will place my "stand" (a three legged stool). I decide when I need to move. I decide when, to go back to the vehicles. I decide to shoot or not to shoot the deer that I see. It is the best time for me