Oh? How so? (assuming it's being enforced properly)
I don't know what you mean by "enforced properly" but just off the top of my head
1) Nothing forces you to answer a question
2) Giving an NPC a quirk such as referring to themselves in the 3rd person can be utilized with a false identity. "The Great Flannegan would never betray his fellow man!" Sounds like it is open and shut truth... but what Zsarl says about the Great Flannegan doesn't apply to Zsarl
3) Most people aren't trained interrogators and it is trivially easy to answer questions in a way that sounds honest, but is deceptive. Player's might not catch someone answering "What is your name" with "You may call me Timothy my lords, unless you prefer a different name?" Which doesn't actually confirm the kid's name is Timothy. Or a question of "Do you mean us harm." could be answered with "Not right now, but if you lay a hand on me I'll gut you." Which again, is a true answer, but could obfuscate the actual intent.
4) Magic items that block it, but that's cheap
5) "Well, you never asked" type situations. You could ask "do you mean us any harm in the future" and the person can honestly answer no, but you didn't ask if the demon hiding in their shadow means you harm, so you can't uncover that with a Zone of Truth
I mean, seriously, FEY and FIEND archetypes are built around the idea of misleading with the truth. If you put the effort into it, it isn't hard to do. Especially if player's have to do this vetting with every. single. character.
Now, I'm sure your party of 45 years who have seen every trick in the book could never be decieved by anything like this.... but not everyone is at that level.
More hostile does not necessarily equate to less fun.
Not necessarily, but it often does. That's why "hostile workplaces" aren't something everyone clamors to be in.
Traps are nearly always the right thing to do, but then again I'm in the unpopular minority who actually endorse gotcha DMing from both sides of the screen if the players aren't cautious (and if they are, that caution should be rewarded with a considerably lower frequency of gotchas).
I know. I still fervently believe you are wrong, and the fact that you are in an unpopular minority supports that observation
Information is power. To gather power one must gather information. Result: spies are a common thing.
Also, people are people; and money sometimes speaks rather loudly and persuasively to those who otherwise would be loyal.
And if you murder your inn guests, you make more money. Therefore every 10th inn should belong to a serial killer right? Come on. Half the time the PCs aren't even worth spying on.
As a powerful adventurer I have made a lot of enemies in a lot of places (including, in this character's case, an entire nation). The moment I stop respecting that fact - and taking precautions because of it - is the moment I'm in big deep trouble.
Or we could not equate doing good deeds, helping people, and growing in personal power as an inevitable slide into assassins interrupting your breakfast every third sunday. Because that's kind of boring. And ridiculous.
If I'd got my throat slit I'd be even more careful on my due diligence in the future, you can be assured of that.
Exactly. You wouldn't trust. So the next NPC passes by, and then the next, and it becomes a self-reinforcing cycle where you are constantly on watch for spies and trust no one, so you never actually get the chance to encounter good people or relax. Because relaxation is a knife to the back. No thanks.
If the player bothers to even mention that the PC is somehow vetting the hirelings, odds are very high there'll be no problem and the hirelings will be decent. Fail to take that little step, however, and the door's wide open for me to mess with stuff.
So, even if I bothered, I'd just hand you a pamphlet with the SOP for anything I ever do. And you wonder why I think it is a good thing NOT to do that? Because a single day of being exhausted from work, frustrated because my family issues are bubbling up again, and I forget to mention "oh yeah, I look for spies" and BAM! my one escape from how terrible life is gets turned into a mess of drama on top of all the OTHER dramatic messes.
No thanks.