I came across these tables from a little while ago from the AD&D Forgotten Realms City System, and it intrigued me enough to hang on to it even though I can probably count the number of times I've used it on one hand. Supposedly, there was a longer version that had much more detail (I'm imagining a classic AD&D nested-tables-within-nested-tables type of thing), but this one seems like it would have much more value during a session.
Tables like this one—lightweight, don't require much pre-planning, meant for the players to roll on during the game and not the GM outside of the session—are like candy for old school players. They're fun and enjoyable despite not offering much substance, but too many of them could bog your game down and potentially ruin your supper. Or not, I don't know, I just assume that you can have too many and eventually they'd slow your game down.
That being said, if your players are going to spend a significant amount of time in a city, I feel like tables like this can be as important if not more than any table or method you used to actually generate the actual city itself.
It's good to have all that foundational stuff for a city figured out, but when it comes to actually playing the game players are going to have more contact with the city through activities like pickpocketing than they would if you explain to them which district is which and why they should care. That's probably why tables for carousing and searching bodies and stuff were so popular in the OSR—it's stuff players actually like to do.
Which is why it's nice that there are so many tables like these out there on the internet, because when you have a bunch of them on hand it gives even more motivation for the players to interact with the environment, and gives you a perfect excuse to sneak in some exposition. It's like how I imagine some parents hide vegetables in their kids' meals so that they'll finally shut up about how gross cauliflower is.
Speaking of sneaking in exposition, tables like these all but hand you an invitation to alter and bastardize them as you please. The smudged pamphlet can be from an up-and-coming cult that's going to take over the city in a couple months if they PCs don't do anything about it, or the deck of playing cards can be marked with the symbol of the gang that runs an underground gambling ring. When I DM, I'm always looking for more diegetic ways to give my players leads and information.
I see the value in making your own tables for these sorts of things, but there's something nice about using one someone else made. When you see someone else's table and get that raw mind-to-mind exposure, your imagination gets jumpstart on new ideas you wouldn't have had before. I see on the valuable table "99-00: small non-magical book" and I think about how small the odds are for that to be rolled and then I wonder what if books were contraband in the city. Or what if all the books were the property of someone important, like a mad wizard king, and he can secretly see and hear through his books if they ever leave his library. And now he's got a bead on you since you were unlucky enough to steal it from some other sucker.
It gets the mind a-firing.
Anyway, there has been a lot of controversy in the OSR over the past few years, so I decided to take a brave, noncontroversial stance and say that random tables are good.
Also, I tried to do some research to see if thieftraps were actually a real thing, but I couldn't find anything conclusive (after about a half-hour of googling). I like the idea, especially as an added risk to the pickpocketing PC, but in actual practice they seem like more trouble than their worth. I would feel sorry for the poor sap who absentmindedly reached into his pocket to grab something else, only to get his fingers caught in his own trap. How humiliating.