It comes down to individual values, yes? Some of it is generational - my guess is that many more people stayed at the same job, ordered the same donut each morning, and never strayed from Aunt Jemima or Sears. Those of us who are younger are going to have varying degrees of loyalty, but because of how the world is and was when we grew up, it's probably not got the same importance. Personality is certainly some of it, too. Me? Brand loyalty is much less important than many other things.
Someone early on in the thread asked why it mattered. The same reason that someone doing something differently than we do freaks us out at times. When someone does something and it's not like we do (or think), we notice. Probably related to evolution and our survival. We need to notice people acting different. And, almost all of us have a hard time accepting values that are quite different from our own. Our best friends and lasting mates usually have values similar in many respects - we keep the same amount of clean, think about work, saving, sex, religion, etc. very similary. The more different we are, the more we fight. The more different, the harder to "let go" and let them be/think/act in ways they value and we don't.
When it's our mom or dad?????? That's even worse! For me, it's my MIL. She does things that are soooooo antithetical to me that I just shake my head in awe. Our worldview is about 180.
My shopping values are an equal match between quality, ease in purchasing, item interest, good farming practices and cost. My MIL values cost and brand, with item interest only coming into play when cost and brand align. If she loves it and it's expensive, too bad, so sad, she'd not getting it. I might buy early season cherries at $5 a pound because they are delicious and the season is short and I LOVE them, if they at a store close to me and look and smell delicious. But I'd probably go to $6 if they were raised organic. She'd never buy them because they cost more the $2 a pound, her cut off point for fruit. She thinks I'm crazy for buying any of my food at Whole Foods. For me, it's across the street (easy to get to), has things that are both high quality and interest me, and for many items (the 365 brands, for example) are less than Jewel or Dominicks. She goes with me sometimes and looks, but never buys anything! She often holds up some produce and tells me how much she'd pay for it the produce store on Cicero she loves. It's a fine store, but I'd lose more in the trip to get there (I don't have a car) than I'd save. In the time it would take me to get there and back, I could have worked and billed 2-3 hours to a client. She's retired, so that bus trip isn't a hassle and is even fun for her.
I just have to remember that her perspective is equally valid to mine and mine isn't right...it's just right for me. (Even though I'm sure mine must be better in some way

).