I find the concept of the "Klingon Promotion" to be utterly baffling and I don't understand why so many sci-fi and fantasy settings use it. It doesn't make the culture look hardened and warlike. It just makes them look stupid for encouraging underlings to kill their commanders at the first opportunity.
It identifies certain leaders as good at their jobs - when Leader X has been in charge for so many years, and either isn't bumped off or successfully defends himself, it shows that either he's a Certified Badass or his underlings like him (presumably for being successful). It also lets you potentially identify Good Guys, who
don't Klingon their way up the ladder and just advance normally by being Actually Good at their job. Because the corollary to 'anyone can ascend to the top if they can just take out the person above them' is that anyone can be
removed from the top - effectively and permanently - if the people below them aren't happy with the situation. (And not liking Leader X and thinking you can do a better job than him if only you could be in that position is a common fantasy, I think. Side-eyes current political situation.)
EDIT: I mean, the original point probably
was much the point you bring up: it shows the group in general to be short-sighted and barbaric. Some authors might still be using it the same way. I'm just trying to think up reasons for why it might be used in a less explicitly bad fashion. For example:
Let's say that Leader X is sickly, can barely walk, etc. If someone wants to off him, they almost certainly can (especially if the culture has requirements for Klingon Promotions to be official - death needs to be public and using only certain methods, for example). And Leader X probably can't just hire a champion, since that should make the champion the leader. But his subordinates, if they're loyal, probably
can step in and force any challenger to go through them first - and if they're not near-crippled for one reason or another, any would-be challenger might be less willing to try. On the other hand, if Leader Y
is a corrupt bully who's running the country into the ground, then it allows for an
official change of leadership without the stigma of a coup by someone who is more qualified.
I am not terribly familiar with franchises that actually have Klingon Promotions, but I expect there are
some rules/protocols most have to prevent total societal collapse, even if they aren't spelled out for the reader/viewer. Otherwise there would be nothing preventing ... *looks up names* Vaako from just killing Riddick after the death of the Necromonger Lord Marshal at the end of
The Chronicles of Riddick. 🤷