Whats the usefulness or inconvenience of frictional force by turning a door knob?

Since a frictional force is created between the hand and the knob of the door, which led to opening the door. If there is no friction between the hand and the door, then we can’t open the door. It can be proved by applying some lotion on hands and then trying to open the door by turning the knob. The friction will be less in this case and it will not be possible to open the door.