Unlike the rest of the Apple lineup, why don't iPhones make use of USB Type-C?
Apple is notorious for adopting new technologies and setting new standards in the tech industry across a variety of different platforms.
After the release of the iPhone 4S, which was the last time the large 30 pin port was used in the iPhone, Apple helped develop USB Type-C along with Intel and Samsung in order to allow for more slim devices. However, the new USB Type-C standard wouldn't be ready until 2014.
This left Apple in a rather tricky situation in such a competitive market. Essentially, they had a choice of either keeping the 30 pin port in the iPhone 5 and 5S and keep those generations of iPhone bulky like the iPhone 4 generation, or they could release a whole new port, which is what they did with the iPhone 5 and the Lightning connector.
Doing so, however, rendered many accessories for the iPhone completely redundant as they wouldn't work with the new iPhone's, which lead to a bit of an outcry.
Fast-forward to 2014, and Apple still didn't adopt USB Type-C in the iPhones as expected. This was largely due to Apple not wanting to yet again change the connector type.
In 2021, iPhone still doesn't have USB Type-C, and it's highly likely that Apple will never switch to USB Type-C in the iPhone. It looks as if Apple want to go completely wireless as they have with some of their products already, such as the Apple Watch.
Going completely wireless has some benefits as well, such as allowing for more compact and thin designs, as well as durability and water resistance.
Take a look at the video below by YouTube channel, Apple Explained, on Why iPhones Don't Use USB Type-C?