That's nonsense. I use MLS IDs for most counties, if I can get them (since some counties don't have them, though other options exist). There are in fact, usually adjustments for these different areas. But, of course, your comps should preferably come from the same MLS area, in which case there wouldn't be an adjustment. But it often happens that you have to extend your comparable area further out to get a decent set of comps. In my hometown of Pacifica, you have distinctly different areas. South Pacifica is much sunnier and warmer than North Pacifica; you have inland areas without an ocean view, and the more coastal areas with magnificent views. North Pacifica is a quicker commute to work, and so on.
If you don't use MARS, if you have NEVER used MARS, then you don't know the difference. You live at a certain level of ignorance. I have seen the appraisals of so-called Expert Witnesses. Flying by the seat of their pants. I have worked in some respected offices and seen many other reports. Don't you think I know? I do, exactemant.
As to your statement "locational factors relating to social factors," here's the problem: there is almost ALWAYS some correlation between location and racial characteristics. And the law and regulations say absolutely NOTHING about correlation levels. So, when you say "relating," we can take that to mean there are no adjustments to be made among locational factors. That is nonsense. 12% of blacks live in district A, and 14% of blacks live in district B, so B has more blacks than A. This kind of relationship exists everywhere. So, that first statement above is nonsense. Even if you succeed in stating more precisely what you really mean (I would assert you perhaps don't really know what you are talking about), - you will run into other problems.
So, in conclusion, there is almost always a relationship between locational and social factors. Per USPAP, such relationships, based on social factors involving protected characteristics, are to be avoided in appraisals. And yet, appraisals must be adjusted to market conditions. And, in practice, "market characteristic" should avoid protected characteristics, per anti-discriminations laws (FHAct, ECOA, Civil Rights Act, 1866, etc.)
The primary factor that trips up appraisers is the additional avoidance of "proxies" as replacements for protected characteristics. A somewhat grey area that can lead to contradictory requirements for the appraiser, which must be resolved through case law and other jurisdictional proceedings.