When I was younger, I never bought adventures for role-playing games I owned. "I can come up with this stuff on my own," I would tell people. "Not only that, but my players never follow the expected plan, and I wind up with PCs who are off on their own somewhere."
Over the years, however, I've softened. A lot. In fact, if a particular game's designer writes an adventure, I'll seek it out more often than not, because more than anyone else, a designer will know what the game is about.
"Old School" games tend to be more straightforward - kick in a few doors, kill some monsters, liberate some treasure, and get back alive. But, even then, there were often nuances that players and GMs would miss. Newer games have grown more and more esoteric - in some ways, it's a good thing, but in other ways, it's a terrible thing.
I was reading a game the other day, and when I finished the rulebook, I set it aside and said to myself, "Yes, but what is the game about?" Because the rulebook really didn't help much, and they hadn't included a sample adventure of any sort.
There are games which are designed to be spun up on the fly - World of Dungeons, for example, is the single most straightforward game I have ever seen. No guidance is necessary.
That's not to say that only bad games give you no guidance about where to go, either - some of my favorites guilty of that - Blue Planet, for example, gives you one fully-developed world complete with ecosystem and cultures to play with. But it's not clear if they want you to play native insurgents fighting against the wave of prospectors and other immigrants coming to Poseidon or if they want you to play a Shadowrun-style game of hacking and looting the big corporations. Or if they want you to be police officers or fighter pilots or space-jockeys. Or Frontiersmen or settlers. There are too many options, and the GM has to communicate clearly with players before character generation.
Contrast that with Dogs in the Vineyard, where you play a Dog - essentially, a cross between a Marshal and an Inquisitor, out to protect people from the results of their sins. Set in the Western-feeling area known as Deseret.
Last night, we played Motobushido, where you play a motorcycle-riding samurai who was a member of the losing side in a recent war. As part of character generation, you decide what the war was - how long ago it was, what it was about, and what the results were. Our GM (or, sensei, as the game terms him) was none other than the designer himself.
Having read the playtest documents, I was pretty clear on what the game was about. In fact, it spells it out in the first few pages, "This is a game about death," it says. It explicitly spells that out. The paragraph continues, "The true motobushi lives his life and performs his tasks as if he is already dead, and thus has nothing to fear from the spilling of his own life’s blood. The mechanics of this game allow seven possible ways for your motobushi to die, all of which you can easily prevent, but none of which you should actively avoid."
I'd say that spells out pretty quickly what the game is about. But the fact that the GM was also the designer was an additional bonus.
A lot was chopped - in part because we were chatty and sociable and had a good time outside of the game - but we got a feel for the mood of the game (and with an RPG, sometimes the mood is the important thing).
... and the Red Right Hands will probably appear in some form in the next post-Apocalyptic game I run. I think they could even fit nicely into Apocalypse World.