because the service is strictly server-sided. While you can sideload the official Apple Music IPA file to a device using various tools, this will not grant you a free subscription or offline features without a valid account.
This is a critical section of the guide. The source of your IPA file is the single most important factor in maintaining your device's security. Apps from the App Store undergo a review process; sideloaded apps do not.
This comprehensive guide covers everything you need to know about sideloading the Apple Music IPA file onto your iPhone or iPad safely and efficiently. What is an Apple Music IPA File?