"This is not fair!" said the Russian after looking at a map when they realized that they were not at the state fair.
I don't remember precisely how the joke goes, but it goes something like the above. I was thinking that the reason why the joke works is that, in Russian, one can distinguish between nouns and predicative adjectives, even though no articles are used, because the two are declined differently.
Это -- не честнo!
Это -- не ярмарка!
In contrast, when one translates the above two sentences into English, one relies on the presence of an article to tip-off clearly whether the predicate is a noun or a (predicative) adjective.
Does the fact that both nouns and adjectives are highly declined in Russian, and moreover declined differently from one another, enable Russian speakers to get by without articles?
EDIT: Looking at the comments and answers to this question, it appears more likely that Russian does not have articles because of the declension of nouns. Of course, technically speaking there is no evidence for "why" articles are or aren't in any given language -- the comments however do note an apparent correlation between the declension of nouns and the absence of articles, as well as between undeclined nouns and the presence of articles, in several branches of Indo-European languages. Still, we are talking about a sample size of at most n=4-7, so nothing definitive.