Well, the other part of it is that there has to be a continuously evolving set of challenges. I mean, within a few months of starting to play D&D I drew up a sheet, it was the 'door protocol', and it stated what was meant when the character's would 'sniff and listen'. It was a whole fairly elaborate process with various contingencies which accounted for all the silly things that DMs had thrown at us, and our extrapolations thereof. So it included an examination of the area in front of, above, and around the door for all sorts of possible factors, followed by inspection of the door itself, listening (with an ear horn, no ear seekers allowed, thanks). There was also a rot grub inspection and protocol, etc. etc. etc. We even verified that the door was not a mimic.
The point being, it wasn't much of a skilled game at that point, unless the DM invented some new twist that was calculated to fall outside the sniff and listen protocol. DMs in that sort of paradigm cannot stand still, they must invent ever more preposterously elaborate and unlikely challenges. You can see the outlines of this arms race in the rules themselves. In the start a door with orcs behind it was probably enough, then it needed a trap that did a bit of damage, and then a lock, and then a bar, and then poison, and then an ear seeker, and then a rot grub, and then finally doors that were mimics, etc. etc. etc.
So, again, like the example of chess, the gamist avenue of the DM challenging the players MUST eventually devolve down to merely a contest of mental fortitude and such between the players and the DM. This obviously creates a strong impetus for unprincipled play.