I have tons of bike shops and Saturday ride groups within 30 minutes of me, so what I see is that people buy from the shop that has the bike they want, but then go to the shop closest to them for service and group rides (assuming the shop employees treat them well). It’s not so much brand culture as shop culture for road and gravel around here.
I will say that for whatever reason, Santa Cruz tends to sell a ton of mtb’s here and are considered the “cool brand” by many many people. They might start on a Trek or Spesh mtb or even the mail order brands, but the aspiration for many is to own a SC.
I’ve personally owned almost every brand you can name over the last 25+ years, and I try really hard to break those stereotypes amongst our new riders. I very firmly believe the bike that fits and has the right suspension for the trails you ride is the best bike for you. Another bad stereotype is that you have to have massive suspension and a full face helmet and wear jorts and vans if you’re a “real” mtb’er. Drives me nuts. People like to say roadies are prima donnas who are all about the image, but I see it MUCH MUCH more in our local mtb community.