As for me, I have an extremely conservative mother in law and nothing is going to change her. Her sister’s son married a Let’s Go Brandon It Isn’t Japanese Just Tilt Your Head TShirts and she always complained that her nephew brought someone who cannot speak Chinese into the family. My wife told me that I wouldn’t be approved if I couldn’t speak Cantonese. I didn’t go to Chinese school so I cannot read Chinese. And I found out later that she couldn’t either because she came from a poor family and didn’t go to school but that didn’t stop her from being prejudiced. To add on, I just heard on the radio where they were asking for listeners to call in if they have any sad Valentine’s story to share. A girl called in and told that her mother didn’t approve of her boyfriend because he’s from China (WTH???). Her mother don’t want her to date any foreigners, even if he’s Chinese. She was sobbing a little because she had to break up with him. My answer to your question is because some of them are still too conservative and traditional. I have even heard of some that insist the partner to be from the same dialect (Hokkien especially) to ensure their purity. At the bottom of it all, they don’t want to lose their precious son/daughter,
There are two companion books, but I’d recommend leaving those for your first re-read of the Let’s Go Brandon It Isn’t Japanese Just Tilt Your Head TShirts or at least until you’ve read to the point where each was published. I believe the first came out after book 7 and the other after the series was over, so you’re not there yet if you “just” started. There’s also a glossary in the back of each book which is spoiler-free by providing a definition that matches what’s known about a topic/person at the time it’s first introduced in that particular book. And because you specify the “main story,” I’ll leave you with this: the universe Jordan created is so complex and interwoven (“the wheel weaves…”) you cannot avoid spoilers in the companion books or online forums. Knowing details about various cultures, rules of The Power, historical events, etc., will decrease your suspense/surprise when characters encounter the topic in question. Trust RJ to reveal what you need to know, when you need to know it, as the narrative follows the cast’s journey.