Apple initially refused to replace my battery because they're consumable, even though they later admitted that some batteries were defective. They replaced some batteries for free [1], everyone else got an iOS 10.2.1 update with silent throttling [2]. Note that Apple did not admit to defective batteries until late 2016, and then announced an update with silent throttling in early 2017.
I am not implying that Apple should replace everyone's batteries for free, I am however under the impression that they attempted to keep warranty costs low by denying for as long as they could, and quickly following up with an update that hides the symptoms.
[1] https://www.apple.com/support/iphone6s-unexpectedshutdown/ [2] https://techcrunch.com/2017/02/23/apple-says-ios-10-2-1-has-...
The point I am making is that NO manufacturer replaces naturally degraded batteries for free. Defective sure. And not just phone manufacturers but I haven't heard of any manufacturer doing that. Batteries are a consumable item.
I do agree however that Apple should have been upfront about their measures they were taking to mitigate battery degradation.