I feel like people underestimate the time something will take but overestimate the actual effort. What you say seems to be a consequence of that.
We underestimate the time, because in reality we often worry about things, and procrastinate on decisions. But in the estimate we don't think about it, we assume all decisions will be made immediately.
We overestimate the effort, because we sometimes do not know how to solve certain problems or work efficiently and in the estimate, we only know the hard way, not the easy way. But with practice, the hard way often becomes easy.
It might also come down to us valuing future work more than the work in the past, so looking back things are less effort than looking forward. But in the case of time itself (represented by hit/missed deadlines) we value these as more important with respect to the past than to the future (they already happened, while the future is uncertain).
We underestimate the time, because in reality we often worry about things, and procrastinate on decisions. But in the estimate we don't think about it, we assume all decisions will be made immediately.
We overestimate the effort, because we sometimes do not know how to solve certain problems or work efficiently and in the estimate, we only know the hard way, not the easy way. But with practice, the hard way often becomes easy.
It might also come down to us valuing future work more than the work in the past, so looking back things are less effort than looking forward. But in the case of time itself (represented by hit/missed deadlines) we value these as more important with respect to the past than to the future (they already happened, while the future is uncertain).