It is a milestone in Apple's history. They used Myriad for long before I knew about the company (I'm 19) and since this blog is dedicated to Apple, the header logo is in Myriad, I figured it should reflect their new design changes.
Sure, probably not the greatest reason for the amount of work involved, so it's whatever. I got bored and felt like posting a comment about it lol.
San Francisco is an Apple internal font; no one else can use it besides developers:
Apple restricts the usage of the typeface by others. It is licensed to registered third-party developers only for the design and development of applications for Apple's platforms. - Wikipedia
I'm not upset. Just curious, you guys chose Myriad as your logo to match Apple's lettering? It's interesting that it's not licensed outside of app development.