Yeah well nVidia is the current king of video cards, and people paying $1000 are buying the brand new card from them. I see a lot of the same mentality with people who just buy brand new cell phones all the time. There has always been a group of people who always bought new video cards, but it seems more amplified because of youtubers and streamers talking about it.
Asus is fine for boards. My absolute favorite was Intel. Microstar is nice also. But these are just my own choices, they aren't recommendations. In general, the big ODMs are all about the same. People get their own loyalty based on past history, whether they had issue with the ODM or the manufacturer. For example for past experiences, I won't buy nVidia graphics cards, or video cards from Microstar, even though they are generally fine for everyone else. There is some brand loyalty happening but you just pick whatever works for you I guess.