If you're a dev team that creates Mac/iOS/iPad/etc apps, you might want Mac hardware in your CI/CD stack. Cloud providers do offer virtual Macs for this purpose.
If you're a really big company (eg. a top-10 app, eg. Google) you might have many teams that push lots of apps or app updates. You might have a CI/CD workflow that needs to scale to a cluster of Macs.
Also, I'm pretty sure apple at least partially uses Apple hardware in the serving flow (eg. "Private Cloud Compute") and would have an interest in making this work.
Oh, and it'd be nice to be able to better sand-box untrusted software running on my personal dev machine.
Private Cloud Compute is different hardware: https://security.apple.com/blog/private-cloud-compute/
I would cal this "Apple Hardware" even if its not the same thing you can buy at an Apple Store.
In my experience, the only use case for cloud macs is CI/CD (and boy does it suck to use macOS in the cloud).