I really cannot imagine why people have this behavior. I was often treated unfairly in life, so I try to architect systems that attempt to avoid my perceived unfairness so that the next generation does not have to suffer similarly (ideally in way for which correctness can be shown in a mathematically rigid way).
That, in a nutshell, is why a lot of abnormal psychology is so very sticky. It's even worse than that, however. It's more that most people are just a tiny bit "like that," and no one thinks about it from that perspective.
But seriously, I agree with the top comment about interviewing at Google, and as far as the military academy "hazing" it's generally misunderstood. It's very, very rare for an upperclassman at my particular school to be cruel in the movie-sense, or what I think is the stereotypical fraternity-sense. More common is an institionalized set of standards for the freshmen that may seem overly tough or even arbitrary but serve several purposes: a) they give the freshman a crash course in being accountable for details, b) they give the upperclassman a crash course in enforcing accountability and holding others to high standards, and c) they create a sense of shared hardship and camaraderie. These are actually all very important lessons before a second lieutenant takes on responsibility for decisions that could mean life or death for his or her soldiers (which, in the case of my graduating class, was a reality for us as quickly as 4 months after graduation). You have to force the upperclassmen to come out of their shells and make the freshmen wear their uniform correctly, or make their bed correctly, etc. so that when they graduate they will have the courage to tell their soldiers that they really do need to inspect the vehicles, or maintain the weapons, or wear their safety gear. It takes practice to be accountable for standards on a team. It's not supposed to be about making people suffer for the fun of it, but of course there are jerks everywhere.
Or in the words of the freemasons, order through chaos.
Once hurt, few seem to have enough integrity to break the loop; so it snow balls nicely all by itself.
In that moment, you face a choice. Either you do the same thing that was done to you, or you don't.
If you break with tradition and avoid doing whatever it is, you will end up asking yourself why, and you'll have to answer "because it was abusive". It some cases, that thought may be too horrible to even admit into your mind, or at least it's unpleasant enough that you prefer not to deal with it.
If you go the other way and stick with tradition, then you can just do whatever it is, and you can say this happened to me, it's normal, it's part of the natural cycle of things, etc.
Also, sometimes you are blindsided by this and don't realize you're making the choice until the moment it happens, so you don't have time to mentally prepare to do the harder thing.
Point being, it's not always sadism. Sometimes it's denial.
TLDR: The corollary of "that would be abusive" is "I've been abused". It hurts to confront that possibility, so people look for ways to deny it. And the organization offers them one.
What did (or will) my successors do to deserve having an easier time than I did?
(Disclaimer: have not been to a military academy or a frat; but only to an undergrad school.)