It’s typical for Apple, or any other tech company, to discontinue old models as they introduce new devices. This time around the company kills off four devices from its lineup: the iPhone X, the iPhone 6s and 6s Plus, and the iPhone SE. These four phones are no longer available on Apple’s site. It seems surprising that Apple killed off the iPhone X less than a year since it was introduced, but it also seems logical with the new iPhone Xs carrying the same base model price but with better specs. Perhaps Apple didn’t want to make the iPhone X redundant.
As for the other three devices, having them taken out of Apple’s lineup means we’ve seen the last of headphone jacks on iPhones. The 6S models and the SE were the last iPhones to carry the audio port. The SE is also the last device to carry the style of the iPhone 5 and it was popular with consumers who wanted a relatively inexpensive and smaller iPhone. Right now the smallest and least expensive iPhone option is the iPhone 7 but this has a 4.7-inmch screen compared to the 4-inch one on the SE and is US$100 pricier than the SE at US$450.
Source: Insider