Would you scrub just one side of your face and leave the other side dirty?
Of course not!
Well, that's basically what you are doing when you are not flossing.
Brushing can only clean the visible surfaces of your teeth, but if you want to get to those hard-to-reach places and make sure you remove plaque effectively, then you'll need to floss.
Of course, most people are aware of the benefits of flossing. However, it's estimated that about one-third of Americans lie to their dentists about their flossing habits.