I'm only speculating, but a couple of things come to mind. Although they're getting better and hiring, Apple has in general struggled with cloud, and Spotify li

I'm only speculating, but a couple of things come to mind. Although they're getting better and hiring, Apple has in general struggled with cloud, and Spotify likely has more expertise and talent there. It's not clear to me how much, but there appears to be quite a few pieces of the old iTunes codebase lurking around. I wonder how much of the backend has also been repurposed for something it wasn't designed for, making it difficult to work with.