I don't think that's especially true. Rather, I think that the earliest versions of the game specified less, and groups played with whatever rules and settings made sense to them.(A)D&D has, for much of its existence, sort of assumed that rightly or wrongly it had to be "all things to all people."
Largely agreed.
That said, within the overall fantasy/sword-and-sorcery genre* I think D+D should try to cover all the bases or at least as many as it can; I think it did so reasonably well at one time but not so much now.
* - as opposed to sci-fi, western, modern, etc. - those aren't what D+D does.
Lanefan
No version of D&D is ever going to be "all things to all people," but some can be more things to more people without hurting the quality of the game for those people with specific tastes.
Given the discussion so far in this thread, how about the following thought:
Between it's own design and the OGL that accompanied it, 3E tried to be everything to everyone.