What are earthbound-spirits and where do they go?

Some people are earthbound. 

All their interests are there―

They return for that contact with men and the old conditions they crave.

I know it is difficult to understand why discarnate souls should still hanker after material, and sometimes gross pleasures. 

It is because while on earth their senses ruled them and stamped and coarsened the soul, instead of the spirit refining and purifying the body.

―Spirit Claude