I read the story. It claims to be "a product of a highly focused, laborious effort to write a song that was extremely simple to sing yet musically interesting and emotionally expressive, undertaken by a composer and an educator who happened to be sisters."

I still don't really buy that it was "laborious effort." And I don't think the song is popular because of some fantastic musical merits. If the song was still "good morning to all" then it would be just another song. The only reason it has any monetary value is because it became associated with birthdays.