If you want to tune your core voltages then isn't that what Android is for?
You cannot make informed purchasing decisions if manufacturers are hiding this kind of information from you. How many people bought a new iPhone due to degraded performance when a new battery would have fixed it right up? People didn't have the information to make that choice, and I believe that's what's upsetting at least some people.
Wasn't it obvious to Apple that batteries start to suffer from degradation over time? Wasn't it obvious that the solution to this was the replacement of batteries? If so, why didn't they implement a replaceable battery?
When it starts not just-working, that shows up in the experience with the device, and it no longer makes sense to tell people they shouldn't be asking questions.
When you pay a lot of money for a high performance phone (which is what all iPhones are when they're released), you also expect it to perform accordingly for a reasonable amount of time.