Apple has been accused of slowing people old iPhones in order to sell them new ones. And that accusation is ridiculous. The reality is that Apple does slow old iPhones at times (peak performance) in order to EXTEND its life not to reduce it.
See Apple official statement: A Message to Our Customers about iPhone Batteries and Performance
All batteries degrade over time and can cause the device to shut off randomly, not be able to hold a charge or not power at all. In order to reduce this problem, Apple implemented a software feature that reduces the stresses on the battery at times.
People looking to sensationalize anything Apple related had been spreading the false narrative that Apple does this to sell more phones when the fact is that iPhones remain usable over 2 times longer than comparable high-end smartphones running Android. And this is thanks to Apple looking to maximize the battery life.
The One Apple Failing
If Apple is guilty of something is in not making this clear at first. A lot of people didn’t know they could just replace the battery on their old iPhones and bring them up to speed. This is been addressed on an incoming software update that will give the user more information on the state of their batteries.
A great solution: Battery replacement for just $29
If you notice your iPhone been slower, shutting off randomly even when the battery says it has charge left that means your battery is bad and putting a fresh one in will drastically increase your iPhone performance and extend its life.