Whether or not a word or expression is "obscure" is a value judgment made by a speaker or hearer. Urbandictionary has vast numbers of obscure words, and the nightly news regularly uses many obscure constructions, where some speakers cannot easily reconstruct the original communicative intent. There are many reasons for using "obscure" language. One is that a speaker may consider the linguistic entity to be "ordinary", and is unaware that their interlocutor considers the entity to be "obscure" (or at least, doesn't know what it means). I assume that you know the meaning of "interlocutor", but I could be wrong – I don't know you from Adam (and I don't know if you know that expression).
If I knowingly use an obscure linguistic entity, that is, use a word knowing that the other guy ("interlocutor") doesn't know the word, then I might have in mind putting you in your place, but I might also have in mind educating you about some subject.
The meaning that you seem to assign to "obscure" is obscure to me (since you exclude terms-of-art used in an "appropriate" context, whereas in my opinion, "aglet" is an obscure word, just like "godown" is). My guess (you can tell me whether you agree) is that it didn't occur to you that your use of "obscure" is obscure (from my perspective), so you were unintentionally obscure. The investigation could continue by asking whether it is reasonable to think that every person knows the meaning of psithurism, squalumose, aglet, godown, epagoge, obscure or crunk. (I'm also considering the possibility of some mixing of "obscure" and "obsolete", where "obs." in dictionaries abbreviates "obsolete").
Wun uv dhuh reezuns wee doant ruhform Inglish spelling to be more transparent is that it would make a millenium of literature completely inaccessible. Dictionaries include words like "psithurism" and other words that are probably very rarely used (once a year, ever, anywhere?) so that if you read a book that says "Psithurism of multitudinous leaves made ghostly music" you will have some idea what that means.