Most of us buy branded items because we have become comfortable with them; we are used to them and we don’t want to take a chance on an unknown. I have been disappointed by generics on many occasions, though lots of them are fine.
I have to say store brands seem to be better than they have been in the past- but maybe I’m swayed by the packaging, which is much better than it used to be.
Buying brands is a buffer against ignorance (although often not cost justified). I heard of a study where they looked at purchasing of an item (over the counter medication) between similarly educated professions, looking at doctors and lawyers. Doctors were comfortable buying generics (as they are knowledgeable about medicines), whereas lawyers buy brand names (as their expertise is not generally helpful in making this purchase).