Disappointed!!

Yesterday I went to checkers in Horzion view and bought Centrum multi vitamins,I took one when I got home,wasn't feeling well and thought maybe it's my body reacting to it differently. This morning I noticed that the best before date is 09/19. Now yes I acknowledge that I'm also in the wrong for not seeing this earlier but my point is,why do you keep expired items,especially medications still on your shelves???? Should they not be discarded when they've expired???