freqsound.com

lkrupp said:

Mac Pros shipped with Mavericks, then came Yosemite. SIP didn’t arrive until El Capitan. I would think that studios would be little motivated to update the operating system if the one running is doing the job for them.

As someone who maintains several classrooms devoted to both Avid's video and audio software (as well as other programs) you are occasionally held back from updating to any new macOS because they haven't made their programs compatible yet, usually for 6-12 months from when the OS is released. Then when they do support a new version (and add new desired features and or bug fixes) they usually lop off support for older macOS versions. Also their file formats change, so not upgrading also means your files may not be compatible with others you must share files with who are on different versions of their software like Pro Tools or Media Composer. I've been an Avid/Digidesign dealer and instructor for over 35 years and see this scenario play out repeatedly.