Well, one could say show me one that doesn't have HDMI as well. And of course HDMI was also originally touted as the new all seeing interconnect, but it never happened because companies didn't broadly support that aspect of it, even if they implemented it at all. It had many benefits for such things over IP/serial/USB, but it still didn't happen due to its capabilities in that area just being mostly ignored. And it was pretty widely supported by some big companies when it came out.
And, as I said, Apple isn't the only player. The Thread Group may well be more attractive to manufacturers, and all they need to be competitive with HomeKit (from the iOS user's point of view) is that the user can control their stuff from their iOS device. The rest is just plumbing to the end user, and not something they will likely be much interested in, in which case it would come down to price, and we know that's not Apple's strong suite.
Whether they actually do any better isn't as important (for the purposes of this conversation) as the degree to which they manage to muddy the waters, and split loyalties amongst hardware manufacturers. Given Apple's notorious level of inbreeding, it may be much more attractive to companies to support hardware that can be supported by any client platform, and get access to an even larger potential market. Whether that market actually ends up existing also doesn't matter wrt to this particular debate.
Anyway, that really is it. I've said all I have to say.