Exactly on this day, September 25 2001, Apple shipped version 10.1 of their OS X operating system. The one they later would rename to macOS.
Exactly twenty-five years ago today. Within all their fancy release presentations and videos there are barely no mentions of curl. In their technical notes page, there is just this short single line with not a lot of explanations:

Ever since then, curl has been an established component, present in every version and every install of macOS done through the decades. When Apple later created iOS, iPadOS, WatchOS etc they also adopted libcurl into their operating systems. Never to provide the API to users, but to empower their own applications and services. (But I have no specific date logged anywhere when that started.)

The first curl version Apple shipped in macOS was curl 7.7.2 which was released in April that same year.
Apple has never used a super recent curl version but they have updated it reasonably well I would say. Sometimes less good.
We are proud to have been a part of the Internet evolution all this time. We are happy that Apple, even if merely implied, has validated us and our way of doing things.
We have never worked with Apple, never received sponsorship by Apple, not had them as customers and except a few rare and mostly failed attempts there have never been any communication between us. We ship a freely available Open Source product that they use and bundle in their products. (It is their choice and right.)