Many have claimed that this is a move that intentionally ‘forces’ the users to upgrade their mobiles yearly, just like those Apple staff that charges you a large amount of money for repairs and say ‘might as well get a new Apple product.’
This accusation came about when users, complaining of a sudden shutdown (their phones randomly shutdown after their battery is half charged) on their iPhone 6 and 7 variants. Apple provided the software update to fix this issue. Users then did a benchmark of their phones when they purchased and after this fix. During these 2 comparisons, they realized that the benchmarks were slower after software updates.
When approached, Apple claimed that they did it intentionally to ensure the phone will run smoothly as their batteries get older. A test with an old phone with a new battery confirms this. When this explanation surfaced, there was backlash claiming that they were not clear on this matter to begin with.
By doing this, users will believe that their phone is slower with age and that they would have to upgrade to the latest model every time when the actual fault was the battery itself.