Isn’t that in fact the primary reason? New iOS on old phone crushes it to the point of being frustrating to use so buy new phone. That’s the pattern of most people I know. Not all. But most. i doubt the battery related downgrade is nearly as impactful as iOS upgrades vs the model. To say that the battery replacement would thwart a new purchase implies that the degradation is equivalent to at least a whole generation difference. That sounds ridiculous.