In Never Let Me Go by Kazuo Ishiguro, why was the children's art collected and why was their creativity encouraged?

The children who grow up living at Hailsham are clones from originals living elsewhere. Public opinion is divided about the value of education for clones because they will eventually die after donating their organs. Miss Lucy is a passionate advocate for providing the students with an array of experiences; she expects to demonstrate their fundamental humanity. Madame has a less positive view of the clones, but she takes charge of the Gallery project as she comes periodically to collect their art.
After they have left Hailsham, Miss Emily tells them that the artwork in the Gallery was evaluated as evidence for whether the children “had souls at all,” rather than to offer a window into their souls as Tommy had come to believe.