"They [players who view the rules as primary] cannot see the legendary being the monster stats represent, but only more and more stats."
--Arthur Collins, "The Auld Alliance," Dragon Magazine #216, page 72
Yesterday, I examined Collins's article, arguing that he (along with others) were witnessing a shift in gaming where more people were being exposed to the hobby before they'd had read the literature that inspired the hobby itself. Collins said that the palates of this gamers "have been trained in some strange ways." I'm inclined to agree. Whereas before the "Old School" approach basically used the rules as supplements, but by the 1990s "New School" viewed the rules as the primary reality for the game.
As Collins's quote above indicates, the RPGs became more about the rules and the statistics rather than representing mythical worlds of adventure.
If this trend hadn't come to fruition by AD&D Second Edition, it did by D&D 3rd Edition. Why? Just take a look at the stat blocks both characters and non-player characters (monsters, so to speak). In 3rd Edition, both were given the same treatment. Everybody was basically a PC, and this required more stats on the monster's part.
Before, unless the monster had a high score in say, Strength, giving it an additional bonus in combat, nobody really needed to know its ability scores.
If you upgraded a creature, if you wanted to keep a semblance of balance, you had do to the math. The experience you awarded depended on the creature's Challenge Level. Creatures, both monsters and characters, became distinctly defined by their attributes. Their attributes determined their abilities and powers, and the amount of XP and treasure the DM should award.
Character creation and building became more about distinguishing one's character via stats--abilities and powers, than through roleplaying (i.e. "my fighter took Iron Will,""Oh yeah, my fighter has Whirlwind Attack, why would you take Iron Will when you could have Whirlwind Attack?").
At times, DMing for 3e/3.5e was just a chore for me. I often resorted to just buying and modifying published adventures to supplement what I'd create on my own. I just got tired of creating my own NPCs and monsters. I even resorted to creating my own monster cards--photocopying stat block out of the backs of adventure, cutting them up, and gluing them to 3x5 index cards.
All of this just demonstrates that the rules and stats in 3e/3.5e became the primarily reality. I didn't want it to happen that way, but it did. But by gum and by golly we still played it. When I tried to run a 1e/2e campaign my players all but rebelled. I'd constricted them with a lack of options. Gah!
As an extreme example of how stats became the primary reality over a legendary being, have you seen the stat block for Kyuss in Dungeon #135?
It goes for two-and-half pages!
Kyuss is supposed to be this ultra-powerful quasi-diety at the end of the Age of Worms Adventure Path. But how can a DM see the "awe" and convey it to his players when he's sitting there trying to coordinate all of Kyuss's skills and powers.
Even the mightiest gods and goddesses in Dieties and Demigods didn't have stat blocks this huge. (The DM often had to chose their spells, but still...)