what do writers do all day?

Many writers will mention a daily limit that they set themselves for writing, in interview JG Ballard suggests that he always wrote one thousand words a day, twice as many as Hemingway, but feeble in comparison to the six thousand that Trollope would write. On that basis Ballard could have written six novels a year which he did not, so presumably not every day was a writing day. Similarly pop / rock musicians now seem to go into the studio to write an album, when presumably they could pick up a pencil any time and write a song. 

Contrary to expectations then, most of what a professional writer probably does is not writing, it is proofing, editing, negotiating, marketing and promoting. Similarly even for a famous singer songwriter, most of what they actually do is probably promoting, touring and performing.