In recent years it has become something of a trope to respond to a question with the stark reply "because noun". For example,
Q. Why can't we burn fossil fuels indefinitely?
A. Because science. [Short for something like "because science has shown this leads to catastrophic climate change.]
Q. Why can't I just skip class today?
A. Because grades. [Short for "because your grades will suffer" or something like that.]
The appeal of this kind of answer, I think, apart from its current fashionableness, is that the grammatical awkwardness forces the questioner to think harder about what you just said. Its brutal simplicity is at once an admonition ("I'm going to explain it to you in one word, because that's all your question deserves") and a statement of finality. The response may be argued and elaborated upon, but in the end it will arrive at the same point.
We were discussing this in chat today, and I feel that the noun in that construction is deliberately ungrammatical, done for effect. But exactly how is it ungrammatical? One-noun answers can be perfectly grammatical:
Q. What did you order for breakfast?
Q. Where did you go to college?
Parts of these responses are not really even missing. Complete statements with subject and predicate would appear not to be required.
However, in the "because noun" construction, it feels as if there is a missing predicate; because seems to demand one, and it's not easy (at least for me) to see why that should be so. That's certainly part of the appeal, because without that sense of ungrammaticality the shock value of the trope would be lessened or abated. But why does the noun feel fine all by itself yet incomplete with the addition of the conjunction because? Do conjunctions always require predicates, even if they are elided? Can this construction be analyzed grammatically in some other way than that it is missing a predicate?
Note: I'm looking for an analysis of the grammar here, not a discussion of the difference between "because noun" and "because of noun."