Hello, Rustam. Welcome aboard. I'm not sure I completely understand your post, but I'll try my hand at giving some of my thoughts on what I think your concerns may be (Now, I may not be making much sense... apologies.
Backgrounds don't completely replace race... at least, not just
race. Backgrounds, to my understanding, encompass pretty much any set of cultural tendencies. So your two human (or elven, or dwarven, or god-forsaken, scum-sucking drow
) characters from two different regions in the Forgotten Realms can still have different backgrounds, with differing bonus skills, bonus feats, and favored feats. Page 16 in my book (I'm not sure what page it is for others, as I have the pdf) gives guidelines for creating backgrounds to fit one's own campaign world.
My understanding of the occupations in baseline d20 is that they were introduced to, as you say, "further define one's... character." In other words, the base classes couldn't always cut it alone, conceptually speaking.
Occupations might have been more necessary in games like D&D and d20 Modern, where a character's class(es) dictated available skills. In these games, occupations and backgrounds provided new "class skills," which are not a part of the True20 ruleset. In True20, all skills are avalable to anyone and are chosen, without penalty, based on the characters' respective concepts (including the desired occupation). A character's "occupational abilities" are attainable via the roles. Unlike in many baseline d20 systems, a 1st-level True20 character can
be a stealthy assassin who is also a good fighter without the need for external "occupation" or "background" mechanics.
Also, in baseline d20, classes and occupations weren't necessarily linked in any way, and some class/occupation combinations would have been troublesome without a mechanic in place to allow for exceptions. Occupations served to kind of supplement the class abilities and "base" feats provided by that class. At least, that's how I look at it.
If a player of a Smart Hero, for example, wanted to know how to shoot well, he would probably want to take a criminal, military, law enforcement, or similar occupation. In True20, the added layer of an "occupation" mechanic isn't exactly necessary, as the aforementioned hero could instead take the Expert role (to match the Smart Hero's incredible quantity of skill points) and the Firearms Training feat. The fact that True20 characters start out with 4-6 feats at first level, as opposed to d20's 1-3 exemplifies the system's flexibility.
All that said, though, you could easily make occupation, rather than race/culture, into backgrounds, a la Dungeon Magazine's V For Victory
Does that kind of make sense? I hope it helped.
Also, If I remember correctly, archetypes are just renditions of heroic paths from earlier renditions of the True20 system, essentially starting character "classes," preset packages with already-chosen skills and feats appropriate to a given occupation or character type (these might be what you're looking for in the way of character occupations....). I agree with you in that I would have liked to see some archetypes in the main ruleset. Perhaps GR might have just figured that with the incredible variety in available archetypes from campaign to campaign, it might damage the generic, "universal" feel to include archetypes for just one. And given the precious nature of space in core rulebooks, there's no way I'd expect them to print archetypes from multiple setting genres (you know, besides those in the sample settings).
Though it would have been really nice.