An official tileset would just amount to Toady saying "okay, this one's official now" and bundling it with the game; something there's really not much point to.
Considering huge popularity of lazy newb pack and mayday, there *is* a point.
The existence of LNP proves the opposite in my opinion. Since LNP exists, what point is there in making it redundant?
Because it suffers same issues as "mandatory" utilities? Of people waiting for LNP to be ready instead of getting vanilla (And in turn, LNP waiting for dfhack, therapist or mod updates ... and if compatibility breaks between versions, that can take some time).
That's only part of the issue of mandatory utilities. The other issue is that mandatory utilities fill a need which is already fulfilled (in other words, they're needless) and the final issue is that it uses Toady's time which could better be spent on things we don't already have.
Why does not Toady provide API? Because he does not want to be constrained in development by it. I think that those 3rd party things constrain him anyway, in a way.
More than that I think he just doesn't care to bother maintaining something like that. It's not like an API would be inherently constraining, beyond that it would just require more work to keep in line with the majority of the game.
Goal of making them redundant (and thus obsolete) is good one.
A proper API might be handy to modders, but the DFhack system works fine now. As for other things, the one obsolete wouldn't be the currently existing things. Rather, the new redundant "official" version would be inferior - it can't help but be, being much newer - and thus it would be "obsolete" from the get-go.
Anyway, what I'm getting from this is that you want Toady to develop official utilities as a big middle finger to the fans who have been developing utilities all along. I guess if your dislike for people who enjoy DF in a way different from your own is that strong, I can't sway you from your opinion. But I will certainly continue to disagree with it.