Why would the world be dangerous without friction?

Friction allows objects in motion to return to a state of rest. Without friction, an object set in motion would be unable to stop moving.

As Newton's laws of motion make clear, inertia prevents an object that is not in motion from moving but causes an object in motion to resist stopping. Without friction, it would be impossible to stop motion once it had begun. Aside from the extreme problems of movement, many inventions that humans depend on for daily life would also be rendered useless if friction did not exist. Life on Earth would be effectively impossible without it.