It’s really just one of a limited number of licenses which allows the owner of the license to showcase the work and legally regard it as an official work from the artist who first came up with the idea. Anyone can tape a banana to a wall, but only a few can do so and say that it’s an ‘original’.
I agree, it’s very absurd, and that’s part of the point. It’s also obvious too that someone gives a shit since they’re willing to shell out millions of dollars for it. And as far as taping another piece of fruit to the wall, it unlikely to do well because with modern and conceptual art, it’s all about who came up with the idea first.