Definition of art:
"the expression or application of human creative skill and imagination, typically in a visual form such as painting or sculpture, producing works to be appreciated primarily for their beauty or emotional power."

AI drawings are art because it requires skill on how to tell the AI to make the drawings or painting. You can select parts of the AI drawing and edit it to your imagination. It takes time and patience. I appreciate many AI drawings more than non-ai art. 
I don't actually like non-ai painting.

In the definition the key word is "typically" because in the past there was no computers. So that was the main way to make art but now we have computers which gives others a way to express themselves by making AI pictures.

AI is art.