Also, with the regards to the Beatles, a band I love, it has been chatted about before that credit when it comes to songwriting was much different back then now it is now. If the Beatles had existed in the 2010s, how many of their songs would have George Martin listed as a co-writer? Many of them, IIRC. But it was different back then. Fast forward to now, yes, Swift worked with Max Martin and Shellbeck on three albums from 2012 to 2017 (19 of the 44 songs from those proper albums), but Martin is one of those people who will not produce your song unless he also receives a co-writing credit. Take her song Blank Space. If you listen to the demo of it she played for them in the studio on the guitar, the melodies, arrangement and bulk of the lyrics were all in place, yet Martin and Shellbeck received co-writing credits. Why? Because they produced it and poppified it. To be fair, she probably worked with them to maximize the pop qualities and ensure that her transition from country to pop was a success, but that's an example of a song where she didn't need anyone else to write the song. And to their credit, Martin and Shellbeck produced it in a way that ensure it would be huge, and it was, but there is obviously a difference between writing a song and producing a song.