It matters because if the DoJ wins, Apple Customers will be exposed to every single Identity Thief, Data Broker and Scam Artist on the global internet.
The reason why so many people are happy to be in Apples “Walled Garden” is because it provides them with just enough security to function on the internet without becoming a victim.
The only people who do want to break into the ecosystem are the opportunistic arseholes who want to exploit Apples customer base, whether to track their location and sexual health data for profit or oppression, backdoor their financials or even just sell their kids the equivalent of digital crack cocaine in the form of loot boxes in games.