If you follow these cases more closely over time you'll find that they're less an example of humans stealing work from others and more an example of typical human greed and pride. Old, well established musicians arguing that younger musicians stole from them for using a chord progression used in dozens of songs before their own original, or a melody on the pentatonic scale that sounds like many melodies on the pentatonic scale do. It gets ridiculous.
Plus, all art is derivative in some sense, it's almost always just a matter of degree.
Plus, all art is derivative in some sense, it's almost always just a matter of degree.