[That's one reason why] hyper-specific rules aren't always a good idea in a free-form game, like most RPGs.
There's a conflict between those interested in exploring the situation ("simulation") and those interested in manipulating the game abstraction. There can be some cross-over in rules-heavy but "realistic" games, and actually some people equate realism and mechanical complexity.
To keep a rule-book compact
and allow for taking into account the specifics of very variable situations, provision for rulings in place of set rules is invaluable. Even with a very comprehensive rule-book, there can be a lot of wasted text-searching time only to find that nothing precisely fits the matter at hand. Without intense devotion to the Book, that's not a big problem; the prolonged search won't be undertaken in the first place, people preferring to get on with the game.
That frustrates people who are playing the numbers, whose head-space is in the mathematical construct. That was sort of hard to get into when one was not privy to the data in the first place -- an extraordinary situation given proliferation of rule-books to the extent that players are pretty much
expected to own them (which has been widely the case for a long time).
So, there's a reactive tendency to take factors neat. If you let ad hoc modifiers into the picture, then your nominal 55% (or whatever) rating could end up anywhere from 100% to 0% on a case-by-case basis. Circumstances might even weigh so heavily as to overturn the status quo, as in the case of a "brilliant" guy who slacks off and parties while a "not so bright" fellow puts his nose to the grindstone and studies.
"Not fair!" cries the player banking on the points he or she has put into an Intelligence score. What's fair from that perspective is to use the same odds regardless, and then make up a story to rationalize the outcome (however unlikely it may be).
Thus, in a curious way, the "gamer's" game slips toward the "story-teller's".
I think that on balance this has less to do with mechanical design than with players'
relationships with RPG mechanisms. The emphasis in a design and its presentation, though, is likely to have a lot to do with the kinds of gamers who flock to it.
I have written elsewhere that I find the "narrative-focused" association of White Wolf's "Story Teller" games to lie more in attitude than in rules. (I do not have a depth of experience with those, though, having found the system just too clunky for my taste after some early Vampire play.)
RuneQuest skewed one way because of its basically simulation-oriented presentation. The whole business of acquiring and improving skill ratings was conceived in terms of modeling real-life processes of personal development. Quibbles over accuracy and genuine "realism" of the model take a back seat to the priorities expressed. That has much to do, I think, with why the use of skill ratings did not (in my experience) radically change the game from role-playing to "roll-playing" as many old-style D&Ders fear.
Another factor is that, in 1978, the original D&D ethos in that way still informed most gamers of my acquaintance as the norm. The impetus behind a skill-based (rather than character-class and experience-level) game was to apply a different set of tools to character description,
not to make the referee's role more rigid.
Notably missing was the injection of heavy-handed "balance" seen in later efforts (in TFT somewhat, and more in
Champions). If one starts with such a scheme as a goal, then naturally one is going to treat skills in such a way as to facilitate it. If one sees it, through "old school" eyes, not as a desirable feature but as a Harrison Bergeron handicap, then the lack of motive is going to introduce the means only by accident.