Perhaps traders today are inclined to take small profits, rather than letting profits enlarge, because our ancestors, out hunting and gathering, learned to grab the rabbit or pick the small patch of berries, rather than skip the near stuff and go over the hill for maybe a deer or large berry patch.
Those that went over the hill risked giving up the near, good stuff and perhaps not finding much, other than maybe a hungry sabertooth cat. And they didn't become the ancestors of anyone.