I've concluded that spec sheets in advertising are at best excuses, and at worst lies. Most users don't care what the exact pixel count is, they just want enough pixels that everything looks great. They don't care exactly how much RAM or storage there is, so long as they don't run out of it (either "brick wall effect" or discernible slowdowns). They don't care exactly how fast the processor is, so long as it's perceived as "fast enough". If specifications are presented, it's done so precisely to convince the user "this is good enough" ... but if it was good enough, customers wouldn't be looking at those numbers to see if it's at least above some criteria indicating "well, I guess I can put up with it since you put it that way".

That's precisely why Apple doesn't give specifications for as many products as they can get away with. RAM specs are limited to regular computers. Devices with "retina" displays don't list pixel counts any more (or at least overtly so). Given how they're pushing to make storage size irrelevant on mobile devices (iCloud, dynamic app deletion/installation, Photos cloud storage, etc), I expect they'll eventually drop exact local storage specs in most ads (opting for "small/medium/large").