It’s said that when you have a hammer, all your problems look like nails. I’ve noted the same sort of thing happen in my 4e game. My players, as much as I push them, tend to default to whatever their character sheet says they can do. That’s honestly one of the things I like most about old school games. There is very little to tell you what to do, or how to do it.
It isn’t that the games are unfinished, but rather are left for the DM and the players to work things out for themselves, and the rules are there as a framework to support whatever they opt to do. It’s not a bug, but a feature, that there’s so little that’s been filled in for you.
There’s some discussion that the mechanics limit or direct the focus of the game, in that the combat rules tend to make up a bulk of the rules in any edition of D&D. I don’t think that’s necessarily the truth given how little advancement comes from combat, at least in the pre-3.0 days. Rather I think that the potential complexity of combat lends itself to mechanical codification as a way to distinguish it from the more freeform conflict resolution of cops and robbers or cowboys and indians. Of course it really comes from D&D’s wargaming roots, but from that grew a much stranger game, one where combat wasn’t necessarily a good idea.
This is #23 in the 30 Days of Gamemastering Challenge.