The secret is that most gms dont remember. When they are actually relevant, they may choose to look up the rules and incorporate them into the session. Or they wont if they dont feel they are worth dealing with.
Yup. PF's combat system is intimidating (in execution if not concept), I'll concede that. But in the case of PF's off-combat rules, well, I may not change anyone's mind but I'mma defend them. Gamers who express disdain for deterministic systems are common enough that I know I can't speak for everybody, but FWIW a thinner rulebook doesn't necessarily mean concise. From a DM's PoV it can also mean the creators just
didn't spend time on vast chunks of gameplay and in doing so threw pressure on the DM to essentially fill gaps in the rulebook on the fly. For example, sooner or later, someone's going to break shit. It's gonna happen, and when it does,
D&D5's object rules, while shorter, are crap. The AC and damage reduction are flipped so now AC is determined by material and DR is based on size. So, what, trying to bullseye a vial rolling across the floor is just as easy as throwing a brick through a 20'x20' window, because they're both glass? A gazebo is all but immune to axes because it's big*, but I can eventually smash an iron lock if I keep hitting it with my bare fist**? Sure, you can override these with common sense, but these are hardly corner cases.
Of course players will think of trying to destroy locks they can't open, and having to debug rules on the fly means they didn't save any time at all. Ditching bad rules is easy, and some DMs in fact enjoy winging it (bully for them), but I can't wish into existence a playtested rule that was never written. Outside combat, when player ideas start to get unconventional (and they ALWAYS do), the blessing of those off-combat rules changes this:
DM: "Rogue's attempt to pick the lock fails."
P1: "Well hell, why don't we just bash the treasure chest open?"
P2: "Or pry it open in one go?"
P3: "Could be trapped. Maybe drag it around until we figure something out?"
DM: "Uhhhh. . ." (
Do I pull something out of my ass, or try to talk them out of this?)
to this:
DM: "Rogue's attempt to pick the lock fails."
P1: "Well hell, why don't we just bash the treasure chest open?"
P2: "Or pry it open in one go?"
P3: "Could be trapped. Maybe drag it around until we figure something out?"
DM: (Quickly checks ONE section of the rulebook, knows
exactly what to do in each scenario, waits smugly while the players argue)
The players aren't crunching; they're just gaming freeform. The DM needs a resolution scenario for whatever the players decide
anyway, so having rules in place is in fact easier than MacGyver-ing some mechanics (lest they wind up looking like D&D5's). It's not comprehensive (nothing is), but D&D3/3.5/Pathfinder invested a great deal of time thinking about what players do when they're
not fighting. OK, that does give the rulebook more of a crunchy look (the combat does that no favors), but you don't need to memorize the text to benefit from this effort, nor have the players think about it much. It is, however, a very nice place for a DM's bookmark.
*Big objects have resilience; i.e. damage reduction, and, "Normal weapons are of little use against many Huge and Gargantuan objects"
**Lock has no damage threshold for being small. AC is 19 but nat 20 always hits. Iron fist!!!