I think it comes from Depression era kids who found a brand that didn’t create cheap junk and so they spread the word. But of course, that has been co-opted by capitalist pirates who buy a brand famous for quality, gut expensive manufacturing with the cheap alternatives and then count on making a profit before word-of-mouth catches up to them.

Sears retailer. Gibson guitars. Off the top of my head. Thousands more examples over the years.

My guess as for why people do it today was because their grandparents or previous generations did that as a survival necessity but now we are seeing the behavior warped from its original purpose. Like opening and raising your right hand to show you had no weapon became a friendly wave hello nowadays. Maybe that’s not an analogous example but you should get the idea.