A carrier should just be dumb pipes. Slowly, Apple has been eroding the value that a carrier adds (the iPhone Upgrade Program being the single biggest shot fired towards carriers). I would love to never, ever have to deal with a carrier and their scammy sales tactics ever again.
What can Apple gain from being a carrier? Seamless set up of devices and international roaming. In Europe, we already have data roaming across borders and it is incredible to have a device "just work" when I step off a plane. Bringing the "it just works" mentality to the service layer makes a lot of sense for Apple now. Importantly, unlike carriers, Apple doesn't need the cell network in and of itself to make money. It just serves to push the model this article articulates so well.
The biggest barrier they are going to face is the connectivity issue - they can make the best augmented reality glasses or cellular AirPods, or wireless, portable outdoor speakers, but without seamless connectivity, they won't be able to "just work". The rollout of 5G might just be the opportunity they need to execute on this.