Why do songs have words?

'In 1918 the chairman of Chappell & Co., Britain's largest music publishing company, wrote a letter to the novelist Radclyffe Hall. She had complained of receiving no royalties after a song for which she had been the lyricist, "The Blind Ploughman", "swept the country." William Davey replied,

Dear Miss Radclyffe Hall,

I yield to no one in my admiration of your words for "The Blind Ploughman". They are a big contributing factor to the success of the song. Unfortunately, we cannot afford to pay royalties to lyric writers. One or two other publishers may but if we were to once introduce the principle, there would be no end to it. Many lyrics are merely a repetition of the same words in a different order and almost always with the same ideas. Hardly any of them, frankly, are worth a royalty, although once in a way they may be. It is difficult to differentiate, however. What I do feel is that you are quite entitled to have an extra payment for these particular words, and I have much pleasure in enclosing you, from Messrs Chappell, a cheque for twenty guineas.

Davey had commercial reasons for treating lyrics as formula writing, but his argument is common among academics too...'