Too many on HN seem to forget that Safari exists and has a large market share. If you break Safari then no one on an iPhone or iPad can use your site. That's an unacceptable level of breakage for almost every site, and is enough to ensure that if Apple doesn't implement it it won't be used.
Ironically, Apple's walled garden is the last thing standing between Google and total web dominance.
> If you break Safari then no one on an iPhone or iPad can use your site.
A CSS issue is not going to break any site unless it causes interactive elements to overlap or be hidden from view. Most sites do not implement bleeding-edge features for this reason. Those that want to set it up will do it in such a way that there's a fallback for browsers that don't support that function.
Ironically, Apple's walled garden is the last thing standing between Google and total web dominance.