... one of the tests here is editing an 8K video. That's not an every day use case.

There are pro users that don't need anywhere near that much memory.

For example QLab. It's definitely "pro" software - but it's just automation software and commonly used for tasks like sending a 20 character text string to another computer on the network when you hit a button... it can do more complex things but most of the time the cheapest Raspberry Pi has enough compute power (you can't run it, or anything like it, on Linux however).

A MacBook Air would be useless, because it doesn't have HDMI, and that often is needed. Professionals don't want to use dongles.

While most people running QLab won't be too budget sensitive... they might be buying six Macs that won't be used to do anything else ever*,... so since it only uses a few hundred megabytes of RAM why spend Apple's premium prices on 16GB?

(* half of them will probably never even be used, since they'd be backups powered on and ready to swap in with a few seconds notice if the main one fails, which almost never happens)