Because it is illegal to crack DRM, that's why. You should pay for the service to have the right to own a file. So pay for the service, then try to find a software to back-up the downloaded files.

Btw. I read your other post that was closed, and Tunebite does not crack DRM, it can help you get around the DRM, but first you have to be able to play the file, so TUnebite can record it. And for that you must pay at least once