User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-17735225-20130922102619/@comment-17735225-20130922105022

That'll explain the absence of some monsters that never got into MH4

(Diablos, Daimyo Hermitaur, Shogun Ceanataur, Blangonga, Agnaktor and their subs.)

Also I believe they didn't include baggi and giaprey because they're too annoying and might put some player off (which I doubt but hey its Capcom we're talking about here ). Also there's absolutely no reason to put Ioprey and Wroggi in the same game(I think).

Lunastra's absence might be related to some backstory that makes it solo only monster, similiar to how Monoblos is endangered and cannot be fought without village elder's permission. (Maybe Banned can get some information if there is any)

Desert doesn't appear in the game because Diablos and Daimyo aren't in here and normally the desert are flat area of sand (Maybe they can make it into canyons but there won't be much difference from other areas)

The only one which I had no idea why it didn't get included is Chameleos.

Of course these are only my speculations about what the devs might be thinking.