alt Hacker NewsThat it sounds nicer is equivalent to saying that a native speaker uses it this way. There's no why to it; language evolves based on how it is used. The aesthetics are downstream of the fact that this is the way that native speakers use it.
The question is whether there is a rule that we can use to determine the correct way to modify the noun which it modifies. And the answer is ... sort of?
As an argument against the pure aesthetic argument (in the sense that maybe the usage of it is driven by superior aesthetics) we can find some counterexamples. We can say "there are zero marks on this ruler" and we can also say "here is the zero mark on this ruler". Both of these sentences make perfect sense and are immediately parsable by a native speaker. "There is zero mark on this ruler" and "here is the zero marks on this ruler" are clearly both wrong. The difference here is that in one case we are using "zero" to refer to a quantity and in the other to a non-quantity.
Sort of? The aesthetics are almost certainly driven by other factors, including what phonemes are used. Is why "ya'll" is a word in the south. It isn't like we didn't know how to say "you all" or other similar words. Aesthetically, contracting those into a single word was more pleasant for many people.
So, my argument is that you are looking at the words and distinguishing the singular/plural aspect as driving why we say certain things. I'm saying that you can use a phoneme argument for why "there is a zero mark" sounds correct and meaningful, whereas "there is zero marking on this ruler" starts to stretch it.
That is, allow me to rephrase my assertion. Rather than saying there is an aesthetic argument, I'm asserting that the phonemes involved are a larger driver than is given credit. Often with grammar rules backfilled to solidify choices.