What makes a spirit earthbound?

There is a surprising number of people who do not realise that they have passed from the earth in the death of the physical body. 

Resolutely, they will not believe that they are what the earth world calls ‘dead.’ 

They are dimly aware that some sort of change has taken place, but what that change is they are not prepared to say. Some after a little explanation and even demonstration can grasp what has actually happened—others are stubborn and will be convinced only after prolonged reasoning.