Why do people still buy brand-name medicine when the generic version has the exact same active ingredients for half the price??

I was looking at Ibuprofen today and the brand-name stuff was $15 while the store brand was $6. I checked the back and the "Active Ingredients" list is identical. If the FDA (or equivalent) requires them to be chemically the same to be sold, why does the brand name still exist? Is there actually any medical reason to prefer the expensive one, or is it just 100% marketing and trust in a logo?