According to the CDC about 57% of Americans take supplements consistently and spend around 30 billion dollars annually. I believe that deep down most people feel that these would not be necessary if they consumed an overall better diet. There is also validity to the fact that over farming the same ground for the last century has reduced the amount of nutrients in fruits and vegetables. So supplementing a good diet makes sense, and I personally take supplements mostly for that reason; but they have never been designed to be a replacement for quality food.
What I run into often in practice is my patients are taking 4-7 different bottles of supplements per day, and over time they lose track of why they are taking them. They open up a cabinet and see bottles and bottles of supplements; one for Vitamin C, one for Vitamin D, etc—but I recommend patients take a good multivitamin, and skip taking one bottle for each Vitamin/Mineral and save some money.