They still throttle now after the lawsuit, you can just stop it if you want to. Also an important difference with Apple is that the iPhone throttling wasn’t a safety concern.
This is all sound and well and well-known, which is why you design in a safety factor so that you have plenty of margin even at end of life.
Why didn't they? Since no internal Apple discussions surface, I can just speculate it's either,
* incompetence, they didn't anticipate this
* cost-driven decision, despite Apple products being top-dollar devices and even low-range devices work better in this aspect
* design-driven decision, larger battery would mean a larger device
I'm betting the last point. Someone (Jobs? Ive?) had a fixed upper size limit on the device, and at the same time a fixed minimum CPU/GPU performance limit to not feel sluggish.I think they just got a bad batch of batteries or were too aggressive cost optimizing and this was the fix. 5&6 era iPhones never had this problem and their batteries degraded just the same.
Just missing out on such a basic thing is a bit boggling to me. My iphone 4 was working pretty good though, but I was also mostly in the inner city where connectivity is good to begin with.