The most far-reaching bad descisions in RPG design?

[the OOD]

the practice of giving 1 page of general GM advice at the start of a rulebook, and several chapters of system-specific mechanical minutia for GMs. are we trying to make things hard on the kid who picked up a few rulebooks to DM for some friends? a bad/ill-equiped DM kills a game like nothing else in the hobby, and there is almost zero effort made to educate and prepare new GMs. some may be lucky enough to get invited to a group with a good GM, but it took me about 2 years before I found a good GM(once one person is a good GM, it seems to spread to the rest of the group, witch is good).


[EDIT] I have before me a copy of the Dungeons and Dragons 4th edition Dungons Master's Guide. a $34.95, 222-page book providing "a wealth of advice to new and experienced dungeon masters".
the book dedicates 17 pages to GMing fundamentals(counting some of debatable value), 112 pages of system-specific mechanical details such as encounter levels, 25-ish pages on what a campaign is and basic types, 38-ish pages on worldbuilding and a premade town and and adventure.
we can do better. 17 pages of a 222-page book about GMing is pathetic.

(numbers come from a quick skim, may not be fully precise. sample was taken from the closest GMing-reladed book to my desk, witch happened to be this one)