Whether or not you need to be home when a donated sofa is picked up depends on the charity to which you are donating. Housing Works in New York does require the donors to be present at the time of pick-up, and Goodwill's policy varies depending upon the location.
To make things easier for the donor, most charities schedule a pick-up time frame agreed upon by both parties. This way, the donor is not inconvenienced with a long wait or with wondering when the driver may arrive. Housing Works in New York offers online scheduling for sofa donation pick-up from residential or business locations.