Well, now as we speculate, I think that's where that really low average number of sessions comes in. That number is so low, with respect to 1e and 2e advancement, that I don't think the items you list were the problem.
What you're speculating, here, is that if a problem were to crop up at high level, it'd have to do so prettymuch
every time, before it stopped the campaign. That no campaign would ever re-set
ahead of reaching known issues. That's what'd have to be going on in order for the average campaign length to map closely to the point problems begin. That and low-level TPKs would have to be offset by longer campaigns, to keep the average length from being pulled down by /those/.
And, it's a game that'd been out for over 20 years, but your explanation of the data acts as if each and every instance of a campaign ending were a first-time reaction to discovering things about the game as you go.
It's an unconvincing interpretation.
Finally: why?
If not the qualities of the game, why would campaigns consistently re-set before getting out of the sweet spot?
Sure. For both 3e and 4e they do seem to have designed for folks to be able to experience the full breadth of levels in far fewer sessions than 1e or 2e.
And 5e. 5e's exp table speeds through the first few levels, bringing you into the sweetspot, aproximtely doubles the exp to level relative to the standard value of at-level challenges through to 11th, then speeds up again.
Consider: Name other games that actually pull off high level, or high power play in an awesome way, without having issues crop up.
Games that start & end there, like supers, rather than going zero-to-hero. Most slower-exp games with incremental advancement don't break down in long campaigns. That'd include some not-exactly 'awesome' games, like Traveler, and some fairly awesome ones, like Hero.
Heck, even D&D, briefly (4e), managed to be playable at all levels, and epic got pretty awesome.
They aren't common. Most games break at the upper levels of their power curve.
Thus: Do not ascribe to an act of will that which can be explained to just not accomplishing a really difficult goal.
I don't know where you get 'act of will.'
The issue I have with the common wisdom that "people don't play high level" is the circular reasoning/self-fulfilling prophecy where that's used as a reason not to playtest those levels nor offer much nor good quality content for them, which unsurprisingly, leads to folks not playing those levels much. (Even when a version of D&D
worked at high levels, it didn't offer DM guidance & resources for those levels - and didn't stick around long enough for many campaigns to organically reach them, either.)
Anyway, yes, the data you quoted do confirm the common wisdom. They are silent as to whether that was, at the time, due to the game being bad at high levels for the preceding 25 years, (and most of the succeeding nearly 20, for that matter), or due to some essential preference for fighting animated skeletons* and giant rats, baked into the human psyche since time immemorial, or simply due to the logistical difficulty of getting the same 6 people to show up every week for years...
* animated skeletons were one of the things that sold me on D&D, BTW, since they evoked Harryhausen's famed skeleton sword-fights in 7th Voyage and Jason & the Argonauts.
