Why use your fourth finger when blending makeup?

One of the questions I always asked. I never understood why my nan always used to say use your forth finger and you see people always doing the same on you tube videos. I never used to do it as it felt odd and never had an explanation until now. Your forth finger is much weaker and therefore doesn't pull the skin on delicate areas of your face. Straight away I was like ok hmmm.... But it's true tap your face with your first finger then do the same with your fourth and you will feel the difference x