One of the more striking points in How We Decide by Jonah Lehrer is the strong and sophisticated reward/punishment feedback systems of the brain, which people experience as strong emotions. A vital factor incorporated into these responses is expectation. Expected rewards or losses have less effect than the unexpected. Gaps between expectations and reality make the difference. An unexpected windfall of $20 feels good. A lackluster gain of $20 for an expectation of $40 feels bad.
Hence compulsive usage of online package delivery tracking is unlikely to leave the user happy about being well-informed. Each time the user checks the tracking, the expectation is "delivery has progressed since the last time I checked". If the result matches that expectation, the user feels a burst of reward stimulus; in fact, that experience may "hook" the user into compulsively checking again a short time later. If the result doesn't match that expectation, the user feels a loss despite the delivery happening precisely on schedule! The tracking falls into the category of long-term planning with intermittent milestones. If I'm interpreting the book's advice correctly, the better way to make decisions in this category is with reason, the prefrontal cortex. Logistics is more of a math problem ("A delivery truck embarks at 5:00 AM on a 200 mile trip going the posted speed limit, when should it arrive?").
Also, the tracking creates a subconscious illusion of control. Like the sports fan who cheers the home team playing on TV, mere observation is clearly powerless to affect the outcome. However, each time an observation yields a favorable outcome, the brain "learns" that observation is a good tactic. Of course, we know that watching the pot of water won't make it boil, and reloading the tracking Web page won't make a sophisticated transportation network run according to design. This is why someone should resist the temptation to check the package delivery more than twice per day. That's a setup for disappointment and less happiness over time. For some people, a three-week delivery with no tracking at all may actually be more pleasing than a three-day delivery with tracking. ("I forgot this package was on the way. What a nice surprise!")