My DH does this with coffee, breakfast cereal and toilet rolls, all of which have to be of a particular brand. Time was when I just bought a jar of coffee and he drank it, or picked up a variety of breakfast cereals and he picked one each morning, or wiped his bum with any old loo paper. But now, oh no, it HAS to be only this particular brand of coffee, or that specific brand of granola. And loo rolls can only be bought in Asda. And all these are consequently stockpiled when on offer.
I always recall my family laughing at an elderly relative who would only buy a particular brand of sausage and scorned every other brand - she unwittingly became a household joke which we still roll out today, many years after she departed this world!
Why does age do this to some people?