With the advent of the printing press, publishers lost their monopoly over the once labor intensive reproduction of texts, so they pleaded that authors should be granted license over the products of their effort to protect and inspire creation of future works, so that they didn't meet the same fate as the publishers. Instead, publishers, still in control of their distribution monopolies, began requiring exclusive use of those licenses, and by using the printing press themselves, saved all of the effort and expense while preventing artists from profiting beyond the transfer of licenses to them.
There's more than one industry in existence today whose business is being middlemen, and with the increasing ubiquity of internet, online marketplaces, and digital appliances, it's become difficult to justify that these rules not change except by that same old argument- but we won't be needed if you do!