The seller doesn't always need to be present during the closing of the sell of the home but sometimes they might need to be depending on the documents that need signed.
Sometimes a seller is able to sign the documents for closing on the sale of the home beforehand and then may not have to attend the closing later.
The Buyer though always has to show up for the closing of the sale of the home to sign documents.
On conventional escrow closing or a table closing, the seller may be able to pre-sign the deed and other transfer documents.