I think it's because at some point they start to rely on features solely available in OSX
This is the only answer that really makes sense to me. I think it tightly couples with MacOS stuff like sandboxing, whatever codec stuff they're doing, and whatever perf stuff they're doing to make Safari "feel" so fast on the Mac. I think they feel that replicating all of that in Win32 would just be impossible/unsustainable. Still, I wish they'd just make it some kind of "developer edition" thing. It could be a bit janky, even... as long as it was clearly labeled "for developers" or whatever I don't really see it giving the company a black eye.
We're all dependent on Chromium, its devteam and what Google
decides is "best" for the whole world and the Internet. Which
I believe, is certainly a bad thing.
I agree wholeheartedly, and Apple
seems to agree! That's what's so f'ing baffling to me.
Clearly they feel that Safari is an extremely important project; the only thing standing between Google utterly 100% owning the web in every sense that matters. A thing that would clearly be bad for Apple.
Accordingly, Safari on Mac gets a ton of investment from Apple. And clearly Apple feels Safari is so important that it's the only browser engine allowed on iOS.
But, I can tell you from experience, a hell of a lot of B2B stuff and stuff cranked out by small shops is just never tested on Safari. And one reason is that a lot of small shops just don't have a Mac sitting around. And experience tells us that this is the death of a browser. Nobody wants to stick with browser XYZ once some percentage of their stuff stops working. They don't want to run multiple different browsers. It's a pain. They eventually follow the path of least resistance and just use the browser where 100% of their stuff works.