This is part of a message I received from seller central. I am currently dealing with buybox eligibility issues.
Also, I request you to please provide “Postal Codes or Cities” where you are facing this issue fo buybox eligibility. We request you to provide specific values rather than saying all as this is a requirement as per reaching out to internal team for further investigations.
Im curious what my zip code has to do with anything? Any thoughts?
Closer to the customer … therefore faster transit time … thus beats out others within the spectrum of influence based on your zip code ???
Yup
Makes some sense… but the eligibility issue I am facing is for the entire books category. Its been over a year now that I have been dealing with eligibility in this category.
Zip code makes zero sense for buy box/featured offer eligibility…unless it’s a (very well) hidden metric.
Also @Ssiddiqi21, I’m not certain that Amazon is asking for your zip, either. It reads as if they are asking for Buyer zips, which again suggests that they misunderstood your query to be about winning the BB and not eligibility to win the BB (yes, even though their reply includes the word “eligibility”). 
I’m gonna tag @oneida_books to see if he has any insight here.
It is very nearly impossible to talk to Support about buy box eligibility. Maybe take out the “very nearly”. They always take it as a complaint about not being awarded the buy box.
Definitely:
(TFW @oneida_books says “you’re right”) 
In other words, Amazon has decided that we are all psychic and know in advance which POSSIBLE orders will not be eligible for the Buy Box if they ever take place.
The loons (BOTS) have taken over the entire asylum. 
It is easier to require sellers provide identical information for all BBE related issues, asking for zip codes even if it is not relevant.
It is not a bot related issues - this is a major tenet of how to run a bureaucracy. And Big Tech are all bureaucracies other than X which is a personality run company.
I’ve browsed Amazon through a VPN, and a private browser window. The Buy Box winner was different if I was in New York vs. California.