My gaming experience is shaped primarily by two systems, classic WoD and GURPS, and currently trying to take in some FATE experience (been studying it in theory for a while, started playing recently). And a thing that seems to be true of all three is that veteran GMs tend to not be bound by what the system says, but rather adjust the system to whatever is appropriate, such as by flipping optional rule switches, deciding when to use or not use a given mechanic etc.
Maybe that's an unthinkable attitude in other gaming circles. @kviiri