or perhaps people just like what Apple offer and buy the products...
you cant legislate purchase decisions.
many people who buy their first Apple product keep adding to their collection because they like the look and feel and interface. and reduced virus issues.
The DOJ is trying to remove barriers/restrictions on making those purchase decisions. One of the goals here is to try to help create a more competitive environment instead of having one where a company has too much control, power, influence, etc. in a market. Another is to try to reduce or eliminate as many consumer "switching barriers" as possible.
There are people who may like Apple's iOS "walled garden" but that doesn't mean Apple should be able to stifle app access competition, alternative smartphone competition, etc. on a major mobile platform. Even with the law enforced, users will still be able to get apps from the App Store, choose not to sideload, choose to still buy or not buy an AW, etc. This would hopefully also push Apple to make the App Store even more appealing to customers and make iOS even stronger/better for things like sideloading, alternative smartwatches, etc. and thereby make it a better experience for a wider range of people.