The assumption is that there is some obvious way to agree on what quality is and by the same token consign a huge volume to the wastebasket on preconceived assumptions about its worth. "Popularity" is often mistaken for quality as is simply stuff you like for emotional reasons. What is Quality? Its the same sort of question as what is good Art. It depends what floats your boat. Sometimes in amongst the pile of "junk" is a little gem and at times  someone else's idea of "quality" stuff is your idea of cliché and worn out repetition.