And yet if you don't, you risk losing purchases when Apple loses the distribution rights to something. The little cloud download button gives people a false sense of security, but I've lost a lot of music and TV shows by not keeping backups on my hard drive. Apple really pushes this feature, but when you get stung by a removal, iTunes support will say "what, didn't you read the fine print?"
+ I am always afraid that if you sync with iTunes (yeah, soooo 2007) that I am going to lose something somewhere, a file, a tune, image or - for sure - a PDF in iBooks.
I've had so many things "lost" that way. Without warning, or a summary or an opportunity to make my decision.
iTunes sucks, big time.