Taylor Swift re-recorded her old music because she did not own the original masters which were held by Scooter Braun.

“they told me it's because she never owned her older songs they were owned by scooter braun yes and she had like and to this day she just still does not own those songs so she i think she recorded it yeah right and like you have to like spin the track a little bit or like you have to change it just a”