Shadowlord said:So why not be a fair referee and simply guess how tough or easy something is instead of slowing the game down with "petty" rules.
Well, for one thing, there's a great many people who play the game mostly as a tactical wargame. They do memorize the rules (compared to Advanced Squad Leader, D&D is a rules-lightweight), and follow them religiously. That doesn't make the rules indespensible to you, but it does mean the rules probably ought to be there, so that folks have a choice in playstyles.
For another thing, one of the bigger requirements of creating those "great moment" is suspention of disbelief. One of the best tools at the DM's disposal to help the players suspend disbelief is consistency. The player's got to have a sense of exactly what the character can and cannot do, and how likely success will be. Not all DMs are particularly good at being consistent, or generating that sense that the world is predictable unless they've got rules backing them up. Not everybody is good at "winging it".
Each DM has strengths and weaknesses, each campaign has it's own style. There may be many things in a particular rulebook that you will find useless. But the rulebook isn't written for you, specifically. It's written for everybody, to cover many different styles.