What about if I want to use my voice to turn off lights, turn down my AC, or turn on my TV without my phone or watch around?
What if you want to issue a voice command away from home? Fact of the matter is, HomeKit enabled devices will work with Alexa, however non-HomeKit devices won't work with Siri or away from the home (using voice commands).
Most of the cool things people do with Homekit completely rely on IFTTT hackery or homebridge-plugins. I wouldn't call any of that crap reliable. Or secure really, when you have to download stuff off a third party website to have anything cool security goes out the window. Homekit is more secure when you color within the lines, but we are years away from this market being stable enough to have every option (or even a fraction of the options) inside the lines. Meanwhile the Echo works with almost every hub and device, and the Google Home works with all the big players.
My Google Home works out of the box (no third party hackery) with a Smarthings hub with no hacks and no IFTTT. It understands context in a way Siri could never understand. It works with a network of Chromecasts (again, no IFTTT hacks) to serve content on every screen or speaker in my house, even in sync if I want.
Not sure where you're getting this information from. The reason people generally use IFTTT is due defeciencies with the junk equipment they bought, not due to HomeKit. I have a full Lutron lighting setup with EcoBee3 thermostats and Schlage locks, with soon to be added Lutron shades. No IFTTT used in the least. Scenes are set up to trigger a sequence and I have much deeper integration with my components compared to using Alexa or Google. For temperature indoors, I can simply ask Siri, "what's the temperature on the main floor, guest bedroom, master bedroom, downstairs, etc." With Alexa, it wouldn't be straight forward. You'd have to ask Alexa to initiate some other component to give you the response you need. Some are more direct than others, but often times you can't just say, "what's the temperature indoors." The reason is because it doesn't have the tight integration HomeKit has.
And again, what Apple has provided is a secure platform for automation. The reason it took so long to come to market is because the vendors had VERY strict requirements to receive the HomeKit certification. I'd prefer to have a secure automation platform, than some equipment that some manufacture threw together just to get something to market, with security falling by the wayside.
If you want a hacked together system, with security being the lowest priority, you could probably slap anything together to get it to work. However with the advent of IoT, and it becoming a prime target for hackers, I prefer not to expose my home to more risk than needed, which is why I chose HomeKit ONLY compatible devices.
And yes, HomeKit is at the forefront of home automation. They are just doing it right, rather than throwing a half baked solution to market.