Let's hope that they will eventually come around, now that we have the Mac Pro. It's just a shame!
The problem is, the highest end GPUs supported by macOS, effectively require a Mac Pro as a dongle, and in terms of capability to generate and sustain complex VR environments, they're not going to be good enough in either raw performance, or price / performance, to attract enough users to justify Valve's development costs.
If Apple built a slotbox machine that was ~US$2k with a 2080-equivilent GPU, that could take 2080ti & titan-equivilent GPUs (and in terms of equivilence, we're talking about the actual VR game engine performance achieved), and was user-upgradable with standard off-the-shelf GPUs, they'd attract users, and Steam would deploy resources. Apple would cannibalise iMac Sales, but Valve is only looking at potential seats with big GPUs, and upgradable GPUs in defining their addressable market.
That's exactly what happened with the Macbook Pro, prior to the butterfly keyboards. Even if you installed Windows on it, it was a really good laptop (not for VR or Gaming, but the principle holds - it was a premium standard PC, and it brought people to macOS by being a better, no-compromises PC).
But then you read articles like this one:
Looking for an Apple iMac Pro? Discover expert reviews and buying advice, or read up on the latest news and product releases.
www.imore.com
does that mean that even though it's not officially supported anymore, it somehow works? It would be so cool!
Apple supports the Vive insofar as the system will recognise what it is when plugged in, and their apps will interact with it, but the SteamVR system which provides the positional tracking etc is what Steam has more or less given up on, if Cindori's account is to be believed.
Realistically, there's no point is trying to do VR on a Mac - at the moment, the best you can hope for is to spend 5x as much, to reach a lower maximum performance than a relatively low-end machine, with a big Nvidia GPU, running Windows.
A core i7/i9 system with a 2080ti, and a Valve Index - that's your best quality (without buying a headset that costs as much as a Mac Pro) to price ratio VR console, and you can treat it as an appliance peripheral to make / process content. Share its drive and default app save locations across to your Mac (because a lot of VR apps have only rudimentary open / save features - almost like the way iOS apps would only save documents to their own directory).
Remember, your VR experience is independent of the operating system you're using - Mac or Windows, it'll look the same in the VR workspace, there's no standard system chrome or behaviours to prefer the "mac way" or "windows way".
