Opting out can be done right on your phone, through messages: https://www.theverge.com/2019/8/20/20813800/apple-card-pay-a...
Plus in all cases they bury it in the terms and expect nobody to notice/opt out. It is a practice illegal elsewhere[0] and Apple doing something to save themselves money doesn't make them the consumer's hero, it is still an immoral anti-consumer practice that should be illegal.
Now if they required that you select opt in during sign up, that would be quite different. But that's not the case. Instead it is on Page 14/15 on an agreement you don't even need to read.
[0] https://en.wikipedia.org/wiki/Consumer_arbitration#Consumer_...