I use the interdental brushes every night, before I brush my teeth. I never used to use them and when I did occasionally use them, I'd bleed quite a lot. This is a warning that your gums are not healthy ..... after having used the brushes for a little while, the bleeding stopped.
Think of your teeth as having five sides - the top, front, back and two sides. Three of the sides can be cleaned using your brush - front, back and top. The other two sides also need cleaning or else plaque will build up and cause a problem with the gums if not addressed. A quick brush with the interdental brushes will remove any plaque build up.
You might think your mouth is healthy, but the main cause of tooth loss is not tooth decay; but gum disease :(