This has to do with the attitudes of modern developers now. I was working on the guide for a particular game, and some of the team was watching me play. I ended up using a trick I'd found to skip a large portion of a level, and one of the artists asked me afterward if I was going to put it in the guide. I said of course. He then asked me if I could not, because he spent 2 weeks modeling that area, and he wanted people to see it rather than just skipping it.
Because game developers now are trying to give the player an 'experience', and because costs are so high, the idea of having content be unavailable to players, whether that be because of lack of skill, or because of alternate ways to play, is frighteneing to them, so you end up getting a first playthrough where you really do all you're supposed to do, and see most of what you're supposed to see.