It was long regarded that Apple (either jokingly or not) intentionally slowed down its phones right around the time a new one came out. Just over a couple of years ago, Apple admitted that it was, in fact, slowing the performance of older iPhones, but the reasons it brought forth were somewhat reasonable. Apple has agreed to pay the French Government 25 million in fines by the Paris Public Prosecutor's Office following its investigation of the complaint that iPhone users were not informed that iOS updates 10.2.1 and 11.2 would cause older devices to slow down. For lack of informing its...
Source: https://www.gsmarena.com/apple_fined_25_million_for_throttling_iphones_via_ota_updates-news-41435.php