Why is it important for every table to have a primary key?
The big benefit is that the key is very narrow and naturally in order. Every non-clustered index you add by definition also contains the primary key in order to do look ups. So even though it doesn't appear to have much benefit, using an identity column as a PK would still be helpful. 

Also, if you ever expand on to this and add other tables that need to reference this table, you just need the one column for the foreign key.