People just getting into a field like to run code on their personal machines. This can be quite relevant when your code gets a 50X speedup from running on GPU.

This is sort of like saying "people only do web serving workloads on Linux, we don't need web servers to run on Apple machines" to me.

Not necessarily. Many media editing apps use OpenCL to speed up processing. I know Capture One uses OpenCL, and I think Adobe's Lightroom and Photoshop use it also. At this point even Pixelmator and less well known alternatives use OpenCL, too.

Sadly, most companies won't have any choice but to port their app to Apple's proprietary APIs. It's really a net loss for consumers because most of these devs have better things to spend their time on than Apple breaking compatibility on a whim.

I mean, if you're already running decent code or already have extremely good tooling where small examples can be easily sent to other machines. Additionally, debugging code running on other machines is also a huge pain in the ass vs. being able to step through it directly, locally.

Almost all of my (and my lab's) time is spent tinkering with small numerical examples before sending it off to one of the lab machines to run overnight, and using the GPU on the MBP through OpenCL is a huge advantage.

People used to buy expensive eGPUs for those workloads to keep them on macOS.