Idiots are also inevitable part of any culture, but they can at least disguise as eccentric ones at times. Slang cannot disguise itself.
If you are reading a book about criminal events of the 90s you are supposed to know what you are dealing with. That's surely not the type of language you are expected to use when you address a person in the street or converse with your host when you stay in Russia or Ukraine.
You assume that in most cases people cannot relate to what they are asking about and, hence, cannot put it into the section the context suggests. But what if I say that 80-90% of the people asking questions about slang know it is about slang, because:
a) they know it from the abstract of the book they are reading
b) they can't look up these words or phrases in the dictionary
c) the machine translation tools they may use do not understand such language
Even if some of the questions make their way into the wrong section, it won't do much damage to that section. But having questions about aristocratic language of the past centuries and questions about criminal jargon following one another is beyond ridiculous.