dunno if the graphics promo vs real gameplay discussion is still alive.. i just read it.
The promo material was obviously graded the heck out of in 2D post production similar to how film is graded, probably by a professional colorist. The lighting was perfected, and probably recorded frame by frame with everything way beyond "max".
To say the least.. To get that look straight out of the game, without taking extreme grading steps like BF4 that basically remove most color information is extremely difficult. You need immense testing and balancing of all weather, light, as well as every single texture in the game. Off the top of my head, a game world with rich color palette and changing lighting/weather that still looks good and natural, only GTA V has made it so far. And we all know how expensive that was..
It's just a mix of technical and workflow/quality control/manpower/time reasons that make it so hard to pull off.