Hearing the title Suki tte iina yo repeated about a jillion times over a convenience store PA the other day, I got to thinking about the official English translation of the title: Say "I love you." This is grammatical, and captures the outlines of the original at least, but it strikes me as unnatural.
The main reason it's unnatural is that in a case like this English speakers tend to prefer indirect quotation. For example, I think that as a movie title, "Say you love me" is far more likely than "Say 'I love you.'" (Sidebar: For this particular title, you'd want to capture the infuriating smugness of the imperative form -na yo, so "Admit that you love me" would actually be closer. Digging deeper, it's relatively unusual I think in English for a straight-up line of dialogue, one character to another, to be used as a title in the first place, but whatever.)
Dating and otaku-ing myself a bit (okay, a lot), I remember noticing something similar in the first two lines of the original K-on! ending theme. They go:
Please don't say, "You are lazy,"
datte hontō wa crazy [after all, what I actually am is crazy]
Here, too, I think that the natural English sentence would be "Please don't say I'm lazy," or, better, "Please don't call me lazy." Looking it up now, the title of the song is actually Don't say "lazy", which I strongly suspect is a rendering of an original something like lazy to iwanaide, more naturally Englished as "Don't call me lazy." Indirectness!
Why this difference between the two languages? Ultimately I think it comes down to the fact that (spoken) Japanese doesn't distinguish between direct and indirect quotations in the same way as English. The most natural translation of Iranai to iimashita would probably be something like "She said [that] she didn't need it," but structurally speaking a rendering like "She said 'I don't need it'" is just as valid. Japanese simply does not have the relevant pronoun-usage rules or verb morphology to make this sort of thing clear, and it uses to either way (rather than making an optional distinction with a subordinating conjunction like English).
(I say "spoken Japanese" because of course contemporary Japanese orthography includes quotation marks, and their presence/absence can be used to distinguish between direct and indirect quotations. But this is, I think, a purely orthographic thing; in the language itself, the distinction is very shaky.)
This being the case, it makes sense that native Japanese speakers looking to translate this construction into English would go for the simpler of the two equivalents, i.e. direct quotation. I guess it's basically equivalent to the way native English speakers tend to underuse passive constructions when they first start learning Japanese — the active versions of the sentence aren't grammatically wrong, and since they more closely match the structure of the English they come to mind more readily. A Sprachgefühl thing.