Sure, they bought it, it's theirs. That question makes as much sense as asking if car owners should be able to give lifts with his own car.
you've effectively eliminated the creator's control over their work
No, the creator did that by relinquishing part of his work to other(s).
2.1 Rights Granted. Upon payment for Music Content, we grant you a non-exclusive, non-transferable right to use the Music Content only for your personal, non-commercial, entertainment use, subject to the Agreement.
2.2 Restrictions. You must comply with all applicable copyright and other laws in your use of the Music Content. Except as set forth in Section 2.1 above, you may not redistribute, transmit, assign, sell, broadcast, rent, share, lend, modify, adapt, edit, license or otherwise transfer or use the Music Content. We do not grant you any synchronization, public performance, promotional use, commercial sale, resale, reproduction or distribution rights for the Music Content. As required by our Music Content providers, Music Content is available only to customers located in the United States.
If you want to demonstrate that non-colluding third-party beneficiaries can be sued for the breach of contract of a second party, be my guest, though (I honestly don't know).
I think that most copyright owners are interested in restricting the making of copies because selling copies is a source of revenue for them. Revenue with which they buy food, and clothes, and housing, and cars.
When food and clothes and housing and cars are all able to be freely copied just like music recordings and books and movies are, then the makers of media would likely be less interested in making sure they get paid for their work. If they need a new car, they can just copy one, for free.
Many content creators put off users with their stupid DRM implementations. I remember buying a game for some $34 in 2008. But that game had 5 copy limit. Now I am what you can call a "regular formatter". Formatted PC twice, changed laptop and now I do not own license to that game.
Let user make copies, but trust that they won't copy them further.