DirectX was also crappy vendor lock-in, but let's not pretend that the similarities go beyond that.
DirectX was vendor lock-in _from the vendor that owned 80-to-90-percent of the market_. Yeah, it sucked to be tied to their platform, but at least you were tied to the platform that nearly your entire target audience was already using.
Metal is vendor lock-in from a vendor that owns like, what, _maybe_ 10% of the market if we're being generous? And that 10% of the market is a group that largely is already disinclined to care about video games, so you're already unlikely to capture a noticeable portion of that already-small minority market segment.
It's a dumb move, really. Compare that with how Linux has started getting support for games: WINE and Proton are compatibility layers so that you as a developer can still target that 80-to-90-percent of the market and your game will (probably) work on the 1% that run Linux too without you needing to do extra work -- and Vulkan (and OpenGL before it) are ways of targeting _everything_...except of course Apple, but that's only because they tend to take an IE6 approach to implementing standards (that is: either everyone accepts our crap as a de-facto standard, or else we don't implement any standards).
10% of the desktop market maybe, for mobile games Metal usage is much much higher. Practically every 3D game on iOS is using it now.
This is also probably why Apple is holding out. They see their phone/tablet iGPUs getting powerful enough to be in a league similar to those in their laptops and believe that mobile and desktop gaming will eventually converge. Game publishers might not care about the tiny share of Mac gamers, but will they also feel that way about the far more numerous iOS gamers?
There’s been hints of this happening with some games straddling the line between desktop and mobile like Genshin Impact which is often compared to Breath of the Wild and now the upcoming RE4 remaster will run on iOS in addition to the other major gaming platforms.
Mobile gaming and desktop gaming are roughly as similar as Java and JavaScript, or to use another comparison, as similar as spray bottle and a fire engine.
This is true for many games, probably even most available on iOS and Android today, but there isn’t really a reason it has to be true. iOS has native support for great USB/BT controllers (Dual(Shock|Sense), Xbox, Switch, etc) so as long as there’s adequate computing power there’s no reason why it shouldn’t be capable of the same games one might play on a Deck, PS5, PC tower, etc, especially on iPad or Apple TV where the screen being used is larger.
That remains a purely-hypothetical future though. Not something that you sacrifice any shred of present-day market share for, in the hopes that someday all past trends of "smaller-form-factor devices are more limited than larger-form-factor user-upgradeable devices" will be reversed.
This is typical magical thinking from Apple fan user. I have a friend like that. They seem to think that somehow a chip that will be limited to 10w by its thermal envelope design (and even then last iPhone shows that 10w is already too hot) will be able to compete will chips that can use multiples of that with no issues. It seems to come from a belief that Apple is so much smarter and better than everyone else that they can basically make magic.
In fact, even if you would somehow find a way to divide power consumption of current competent gaming system by ten it would still not be enough.
And all that is before talking about the fact that peoples who games for hours on end tend to prefer displays bigger than 6 inchs...
Anyone with functioning brain cells can objectively understand that AAA gaming on mobile is a distraction at best and a waste of ressource when you are not filthy rich like Apple. But Apple gonna use marketing to say otherwise instead of using it's money to offer more competent hardware at better price...
Game developers generally may care to support Metal to get access to iOS, but this obviously isn't going to entice Valve. Valve wants to sell other people's games through their own store, not their own games through somebody else's store.
Or they could actually properly support and maintain OpenGL (or OpenGL ES, even). Or they could offer Vulkan. They don't even need to be native implementations, they could be Metal wrappers maintained by Apple. It doesn't take much.
On Windows you've been able to use OpenGL if you want, literally forever, because there was always a baseline version of it available with the OS (and then if you installed video drivers, you got a GOOD version of OpenGL.) Now you have the option of native Vulkan if you have drivers too. All of this is maintained collaboratively by Microsoft and the GPU vendors' driver teams. You don't even need a GPU, Windows has shipped software rasterizers for Direct3D literally forever as well (and the modern software rasterizer, WARP, is actually quite fast)
And on Linux you can either use OpenGL (natively), Vulkan (natively), or Direct3D (via Proton), and all three perform great and are reliable, maintained collaboratively by the Linux community and GPU vendors' driver teams.
Meanwhile on Mac your option is to write your own custom Metal backend, or hope that an emulation layer you get from a third party like MoltenVK will work good enough for your purposes and won't break when your end users install an OS X update, since Apple is happy to break backwards compatibility for any reason any time they want. If the build of MoltenVK your app ships with breaks you need to integrate a new version and ship updates to everyone.
